We'll bring you all the day's developments. 15:50 Our Washington correspondent, Stephanie Kirchgaessner, sends this: The White House on Friday said Barack Obama was receiving regular updates from his national security team on the "ongoing" situation in Algeria and was "in constant contact" with the Algerian government. The US president discussed the situation with Mr Cameron on Thursday and was in touch with BP's security office in London. An administration official added that the sensitivity of the ongoing situation meant that the White House's top priority remained the security of the hostages and that it would not release real-time updates on the situation on the ground. 15:38 Read the latest analysis by our Middle East Editor, Roula Khalaf: The handling of the crisis by the Algerian authorities is coming under increased criticism. Known for the ruthlessness of its security forces, which have a long and checkered history in fighting Islamist radicals, the Algerian regime is acting according to type - no negotiation, no tolerance, just strike and strike hard. The Algerians" need to communicate - or rather lack of - is also evident in this crisis, says Geoff Porter of the North Africa Risk Consulting. But this is about the worst scenario that could have happened. Algeria is extremely sensitive on attacks on hydrocarbons sector. It's 95 per cent of export earnings. If they lose those revenues, their ability to continue subsidies on foodstuff, on fuel and housing, all that goes away, and they could have social destabilisation. So [the authorities] wanted to send a clear message right away that this is going to end tomorrow. The Algerians might have a big diplomatic problem on their hands, not having informed countries whose nationals are involved of their intention to storm the compound (especially if the number of casualties is high, which we are not sure of yet). But Algerian officials are also arguing that the hostages were about to be moved, forcing them into immediate intervention. In any case, says Mr Porter, Algeria considers that the attack was a result of foreign interventions in Libya and Mali and the government in Algiers was opposed to both. "They see the international community as being culpable in what happened and they would say you can't tell us what to do," says Mr Porter. Algeria is also a fiercely nationalistic country and its officials will also say that the expatriate community has committed itself to the national project and does not have a special status, he adds. There is also speculation in the Algerian media about whether the president and the civilian officials in Algeria are themselves fully aware of what the military is doing in In Amenas. This story from Le Matin, for example, wonders whether the information blackout which is frustrating foreign capitals is tied to the fact that the president is himself so far from the action. 15:24 Here is a picture, courtesy of Al-Jazeera showing some of the Algerian hostages after they fled their captors: 15:14 Here is Le Monde citing an unnamed witness: On Wednesday at dawn shots are heard in the living quarters at In Amenas. The first attack struck a bus that was carrying passengers to the airport. The attack [only?] caused injuries because the buses are always accompanied by security vehicles. The living quarters are right next to a small barracks of gendarmes, who couldn't repel the assault. One of the employees, an expatriate, heard the shots and headed for the men in military dress to seek refuge. They were terrorists who were dressed like that to trick people. The other employees who were in their rooms and around the living quarters stayed where they were to be safe. When there is an attack, the instructions are to stay put and hide. After taking control of the living quarters, the terrorists searched all the rooms looking for hostages, but especially expatriates. Each of the blocks in the living quarters has eight rooms or thereabouts. The terrorists seemed to be of different nationalities: an Egyptian, a Tunisian, and Algerian, a black man, probably a Nigerien or a Malian. Impossible to know how many terrorists there were in total. One of them spoke English with a perfect accent. The terrorists were very well prepared. They knew the site, the living quarters and the complex opposite. They cut off the production as soon as they took control of the facility. The Algerian hostages were in the lobby, a room that serves as a games room, reception and internet café. [At the beginning of the assault] in a moment of panic the Algerians forced the emergency exit, which was blocked. There was a moment of widespread panic. The terrorists, who were in the restaurant at that point, couldn't stop their escape. Between 400 and 600 people who had been packed like sardines were able to escape. 15: 07 Moktar Belmoktar became an Islamist militant from the age of 19. Check out this picture and some great background reading from the Washington DC think tank the Jamestown Foundation 15.02 France Info, the 24 hours news station, has interviewed a number of escaped Algerian hostages who say the militants only wanted foreigners. They came into the bedrooms, they broke down the doors. They were shouting: We're only looking for the expatriates, the Algerians can leave! They rounded up the expats, they encircled them they tied them up. They were all herded into a corner of the restaurant. Le Figaro reports another hostage telling France Info: When they saw the Algerian army taking up position, they separated the hostages: the expats on one side, the Algerians were taken to the foyer. Now we have no news of our expatriate colleagues; [the Islamists] used them as a shield. 14:42 Defense Secretary Leon Panetta, who was speaking at Kings College in London Friday, says the terrorists should be on notice that they'll find no sanctuary in Algeria or North Africa. He says anyone who looks to attack the U.S. will have "no place to hide." 14:40 Reuters telling us that Al Qaeda-linked kidnappers who took hundreds of people hostage at a gas plant in Algeria have offered to swap U.S. captives for two militants jailed in the United States, Mauritanian news agency ANI reported. They named the militants they want freed as Pakistani Aafia Siddiqui and Egyptian Omar Abdel-Rahman, known as "The Blind Sheikh," ANI reported, citing the group's spokesman. The report did not say how many U.S. hostages were being held. 14:37 There are also reports that a U.S. aircraft has landed nearby to evacuate U.S. citizens and that an American predator drone is monitoring the site. A spokesman for the group behind the attack, called Al Mulathameen, warned of more attacks to come, saying Algerians should "keep away from the installations of foreign companies, because we will suddenly attack where no one would expect it." The attack on In Amenas was in retaliation for the French intervention to combat Islamist militants in Mali. 14:34 Britain says Foreign Office diplomatic rapid response team has landed in Algeria 14:25 Le Monde, the French daily, is quoting an unnamed witness to the assault: 14:20 Outrage from Euro MP Richard Howitt, who says the UK government must now consider why it wasn't told by the Algerians. Here's his barrage of questions: After we get the news for which we all hope that remaining Britons affected are all safe and sound, it is right that the question should be asked as to what it was that stopped David Cameron being told of the rescue operation in advance? When Italy criticised Britain for not alerting them before our own Special Forces acted and one of their nationals was killed only last year, David Cameron needs to be careful before ascribing blame elsewhere. I am concerned if there is a failure of political and diplomatic influence from a region where a terrorist threat is present to Britain both at home and abroad. The French authorities have indicated they will conduct their own judicial investigation in to the incident, and it may be that Britain should do the same. 14:15 From Al-Jazeera live: Spokesman for the Masked Brigade is willing to swap captives for two fighters 14.07 Latest from state news is over half of the 132 foreign workers held hostage have been freed. The numbers are changing all the time as new information comes in. 13.54 Security forces have told Algerian state news that terrorist group is made up of about thirty terrorists of different nationalities. 13.38 Algerian state news agency now saying total number of hostages freed is 650, including 573 Algerians. 13.26 David Cameron said earlier (see 11.00) that "significantly" fewer than 30 Britons were unaccounted for. Government officials have now clarified that there are about 10 Britons still missing, reports the FT's Elizabeth Rigby. 13.18 More from London and the FT's Elizabeth Rigby. British government officials are saying that a British plane has landed in Algiers to bring people home and that freed hostages could be returning to the UK today. David Cameron will chair another meeting of the Cobra emergency committee 4pm today. The prime minister has had a total of four calls with his Algerian counterpart - including the one in which he was notified of the Algerian forces" assault on the gas plant only after it had begun (see 11.00). 13.14 Much of the attention thus far has been on Algeria's southern neighbour and the apparent connection between the In Amenas attack and France's military intervention in Mali. But what of Algeria's troubled neighbour to the east, Libya? The FT's Heba Saleh reports from Cairo: The implications of the breach in security at In Amenas extend beyond Algeria, experts say. A resurgent AQIM staging attacks in the Sahara may find it easier to strike in Libya, Algeria's neigbour where security has been dramatcially weakened following the revolt which overthrew Muammar Gaddafi in 2011. "I think to be honest the follow on risk is higher for Libya than Algeria," said Samuel Ciszuk, consultant at KBC Energy Economics. Algeria has a strong army. One successful attack does not mean that it will be followed by other successful ones. But in Libya there is a security vacuum where it comes to government troops. Security is upheld by different militias and there is a larger chance that something could go wrong and the government does not have the resources to deal with it. 13.12 This is the man at the centre of the storm: Photo: SITE Intel Group Moktar Belmoktar leads the group that conducted the kidnapping and is a senior commander of al-Qaeda in the Islamic Maghreb (AQIM). One-eyed and allegedly linked to organised crime, the French call him The Uncatchable. See 10.06 for more details. He is purportedly shown in this footage of AQIM recruits in the Sahara broadcast in 2010 by France 24. 13.02 More news about the Japanese contingent among the hostages. The Associated Press reports: JGC Corp, which provides services at the complex, confirmed seven Japanese employees were safe and 10 others were unaccounted for. Ten non-Japanese employees are also alive, it said. 12.47 Amid reports that Algerian special forces are progressing through the gas complex, more drips of information on the hostages are emerging. Reuters has this from Vienna: An Austrian man who was trapped when Islamist militants took dozens of gas workers hostage in Algeria has been freed, the Austrian Foreign Ministry said on Thursday. Foreign Minister Michael Spindelegger "has been informed by the Algerian foreign minister that the Austrian who was in this situation is safe and sound," a ministry spokesman said. We have no further details as to how he got out. 12.14 In London at the House of Commons, the FT's Kiran Stacey reports that the chamber was in sombre mood this morning as MPs abandoned their constituency duties to hear the prime minister update the country on events in Algeria (see 11.00). The most significant point was that last night, 30 Britons had been in danger, but the number had fallen sharply overnight. Whether those people had been freed, escaped, or were simply missing is unclear. David Cameron's frustration at the Algerian government was barely disguised as he detailed how he had asked to be informed prior to any military operation, but then was only told when an attack started. Foreign office sources explained last night how difficult it was to get accurate information from the Algerians, and that still appears to be the case - several Brits remain unaccounted for. Strikingly, no one on any side of the house voiced any concern over British support for the French military operation in Mali. 12.08 BREAKING NEWS The Algerian government has said that 19 kidnappers have been killed in its operation at the gas complex, according to al Jazeera. Mohamed Said Belaid, Algeria's communications minister, told state media: Those who think we will negotiate with terrorists are delusional. 12.07 Images of the area are scarce but here is an image grab taken from footage provided by Algeria's Ennahar TV that was filmed on December 2-4, showing Algerian army tanks stationed near the gas complex in In Amenas. Photo: AFP 11.55 To Paris and the FT's Scheherazade Daneshkhu, who reports that Jean-Marc Ayrault, French prime minister, says the Algerian military operation is still going at the natural gas facility. "I have just spoken to the Algerian prime minister who confirmed to me that the operation is continuing," Mr Aryault said in a scheduled address to journalists midday on Friday at Hotel Matignon prime ministerial residence in Paris. He also confirmed the death of "several hostages" but added that the number and their nationality is still not known. 11.44 Further to the implications of all this for Angola's energy industry (11.26), Edward Bell, commodities analyst at The Economist Intelligence Unit, sends some thoughts: An attack on an Algerian oil and gas facility is unprecedented in the country's over 50-year history of production. The government had long been concerned about the potential for such an attack and provided military protection for private operations throughout the country's vast Saharan regions. The attack on In Amenas is unlikely to have a lasting effect on Algeria's gas production but the Economist Intelligence Unit expects it to lead to foreign companies viewing the country as higher risk just when the government is trying to make its oil and gas investment laws more accommodating to international groups. Algeria has already struggled to attract companies to invest in the upstream sector, with its last three licensing rounds largely flops because of stringent conditions imposed on foreign companies. Algeria is in need of investment in its hydrocarbons sector to maintain production to meet both export commitments and fast growing local demand. This is just the kind of event that will deter international contractors from putting themselves at risk in a region that is vast and difficult to protect. 11.26 The escalating hostage crisis at Algeria's In Amenas gas field could have medium- to long-term implications for Algeria's hydrocarbons industry and chill investment from foreign companies, analysts are warning. In Amenas, which has four producing wells, supplies 15 per cent of the country's global gas exports. Algeria is Europe's third largest gas supplier after Russian and Norway and produces more than 1.2 million barrels of crude oil a day, according to the Energy Information Administration. "The situation in Algeria has punctured a bubble about the security of Saharan oil fields and every international company operating there is reviewing what to do and how to communicate the situation to their shareholders," Jon Marks, associate fellow at London think tank Chatham House. The importance of Algeria to international oil companies was highlighted by Snam Rete Gas, the Italian gas grid operator and a buyer of Algerian gas, which registered a drop of more than 13 per cent imports of gas from a pipeline coming from Algeria since the attack took place. "Geopolitical risk once again forced itself to the top of the global oil agenda after Islamic militants attacked the gas field in Opec-member Algeria ... shutting in more than 10 per cent of Algeria's gas production," analysts at DNB wrote. Oil companies operating in Nigeria and Angola, sub-Saharan Africa's two biggest energy producers, have long grappled with militants and kidnappers. The Niger Delta, the heartland of Nigeria's oil industry, has been plagued by violence for years, as networks of kidnappers, separatists and oil thieves targeted Royal Dutch Shell and other foreign groups. In Cabinda, the northern enclave that saw Angola's first oil production, separatists have fought the central government since independence in 1975. But both those threats have receded of late. An amnesty for armed men in the Niger Delta drew thousands from their bases in the creeks and bought a lull in violence. Angola's industry has moved offshore and the Cabindan rebels have been scattered by the heavy hand of the Angolan military. The energy security implications of the Algerian attack reach beyond its own frontiers. In Amenas gas field is located near the Libyan border - and some fear Libyan fields could also become a target. All foreign operators have to work in partnership with Sonatrach, Algeria's national oil company. "The attack is the most significant to occur inside Algeria in recent memory and elevates the already high security risks stemming from wider regional instability," Richard Cochrane, Middle East and North African analyst at IHS said. International oil firms reacted swiftly to the crisis, with Spanish, Norwegian, and British oil companies starting to evacuate workers from Algerian energy facilities on Thursday. Spain's Compania Espanola de Petroleos moved employees from two Algerian facilities to the centre of the country, while BP is evacuating non-essential staff. Statoil is flying 40 non-essential staff back to Norway. The incident also highlights the wider security issues for the industry, and if the attack is an indication of reaction to the French intervention [in Mali], it might be sensible to assume that Total operations may be under increased risk, although it is not involved in this incident. Total's operations in Yemen, for example, have been subject to numerous attacks by groups linked directly or indirectly to AQAP (al-Qaeda in Arabian Peninsula)," Peter Hutton, analyst at RBC Capital Markets said. 11.23 Cameron is still taking questions but the main factual point is that the total of Britons in jeopardy has been "significantly reduced" from the figure of 30 that was given last night. 11.15 Cameron: "Those who believe there is a terrorist extremist situation in North Africa and we can ignore it are wrong. We need to understand and give proper priority to our strategic defence review of this country. 11.14 From Oslo, little news from Statoil on the Norwegians involved. The FT's Richard Milne reports: Still no news on the eight Norwegians still unaccounted for. 18 Statoil workers arrived in Mallorca overnight and will be transported to Bergen today. Statoil is sending a crisis team to Algiers today. 11.09 After some words from opposition leader Ed Miliband, Cameron is back on his feet. Three flights left Algeria yesterday carrying 11 BP employees. We are urgently co-ordinating with British and other oil companies in the region about their security. All installations in Algeria are on high alert. On the motives of the attackers, Cameron says it is too early to be precise. But AQIM's threat "is growing." 11.08 Meanwhile, an update from BP: The serious situation at the In Amenas site in Eastern Algeria remains ongoing. The situation remains unclear and BP continues to seek updates from the authorities. BP's priority is the safety and security of our people. On early Wednesday morning we mobilised our full emergency response system, with teams on the ground in Algeria and in the UK working with the situation and liaising with other parties involved. We are in close contact with the UK government and colleagues in Statoil, in Sonatrach and in the companies that are contractors to the joint venture. There is a small number of BP employees at In Amenas whose current location and situation remain uncertain. BP is working with the Algerian government and authorities to confirm their status. We do not intend to publicly comment on details of the number, nationalities or identities of these staff. 11.00 Cameron is, after all, briefing MPs. He has just spoken to Algerian PM and is now relaying what he knows to parliament. The full details are still emerging. The terrorists attacked two buses and then the main complex. It was a "large, well co-ordinated and heavily armed." Probably pre-planned. Two people in the captured convoy were killed, including one British national. Others were taken hostage in separate locations. The precise numbers involved remain unclear. Foreigners of eight nationalities among those taken captive. Cameron was only informed of the Algerian assault after it had been launched. The Algerians believed the militants were trying to flee and had to act. An initial assault was completed yesterday. But the situation is not resolved. Last night 30 Britons were at risk last night. That number has now been "significantly reduced." A consular team is heading to Algiers.