Twenty foreign hostages, including Americans, have escaped from their captors at a gas field complex in Algeria, an Algerian official says.
An Islamic militant group said it was holding 41 foreigners in the complex in the Sahara.
The Algerian security official said those who escaped included Americans and Europeans. He did not give any further details.
Militants attacked the Ain Amenas gas complex 800 miles (1,300 kms) south of Algiers yesterday, taking dozens of foreign workers hostage. Those being held included Japanese, Britons, French, Americans, Malaysians and Norwegians, among others.
The gas plant has been surrounded by the Algerian army and there is now a tense stand-off with the militants.
Some 30 Algerian workers fled the complex earlier in the day, suggesting that the militants are having trouble managing the many hostages they have taken at the vast natural gas complex, the third largest in oil-rich Algeria.
Algerian authorities, meanwhile, were talking with tribal Algerian Tuareg leaders in hopes of mediating the dispute.
The group claiming responsibility - called Katibat Moulathamine or the Masked Brigade - originally said it had captured 41 foreigners, including seven Americans.
Two people, one a Briton and the other Algerian, were killed in the initial assault, which the US defence secretary has called "a terrorist attack." The kidnapping is one of the largest ever attempted by a militant group in North Africa.
The hostage-takers are reportedly seeking a safe passage out of the isolated area, something Algerian authorities have already rejected.
Another Algerian official said authorities are in contact with tribal elders among Algerian Tuaregs, who are ethnically related to the rebels fighting the Mali government, some of whom have close al Qaida links.
The France-based head of a catering company at the plant told French media before the latest escape that some 40 foreigners appeared to be held hostage in a separate area from the Algerian workers.
Regis Arnoux of the Mareseille-based CIS Catering company said while electricity to the plant has been cut, it had at least three weeks of food supplies.
Militants phoned a Mauritanian news outlet to say one of its affiliates had carried out the operation and that France should end its intervention in Mali to ensure the safety of the hostages.
But the militants themselves appeared to have no escape, cut off by surrounding troops and army helicopters overhead. Algerian Interior Minister Daho Ould Kabila said it appeared that the militants were hoping to negotiate their departure away from the area - a notion he rejected.
"Security forces have surrounded the area and cornered the terrorists, who are in one wing of the complex's living quarters," Mr Kabila said.
He also rejected theories that the militants had come from Libya, 60 miles (100 kms) away, or from Mali, more than 600 miles (1,000 kms) away. He said the roughly 20 well armed gunmen were from Algeria itself, operating under orders from Moktar Belmoktar, al-Qaida's strongman in the Sahara.
Yves Bonnet, the former head of France's spy service, also dismissed the idea that the operation was specifically linked to the French action in Mali due to the amount of organisation it involved.
"It was an operation conceived well in advance - spectacular and needing a lot of preparation ... It was not at all an improvised operation," he told the Europe 1 radio. "The operation was probably already scheduled and simply getting all those people into the desert would take several days."
BP, the Norwegian company Statoil and the Algerian state oil company Sonatrach, operate the gas field. A Japanese company, JGC Corp, provides services for the facility as well.
It was not immediately possible to confirm the identities of the hostages. Ireland said a 36-year-old Irish man was among them, and Britain and the US said their citizens were taken, without giving numbers. The Norwegian company Statoil said 12 of its employees were captured - nine Norwegians and three locals. Japanese media reported at least 3 Japanese among the hostages and the Malaysian government confirmed two of its citizens were taken.
In Rome yesterday, US Defence Secretary Leon Panetta declared that the US "will take all necessary and proper steps" to deal with the attack in Algeria. He would not detail what such steps might be but condemned the action as "terrorist attack."
BP said it would not identify staff members who were taken hostage for security reasons.
"BP's overriding priority is to do all we can to ensure the safety of our staff and to support their families during this anguishing time," BP CEO Bob Dudley said in a statement.
Hostages from eight countries
Islamic militants say they have captured 41 foreign hostages at a natural gas complex in the Algerian desert, but there are conflicting reports about their numbers and nationalities. Here is a summary of the latest information on the hostages:
Here is a summary of the latest information on the hostages:
ALGERIA: Hundreds of Algerians worked at the gas plant, but the Algerian media says most have been released. The Norwegian energy company Statoil says three of its Algerian employees are being held.
NORWAY: Nine Norwegians employees of Statoil are hostages, the company says.
UNITED STATES: Seven Americans have been captured, according to the militants. The US says its citizens are involved but has given no numbers.
BRITAIN: "Several" British nationals are among the hostages, the government says.
JAPAN: At least three of the hostages are Japanese, according to the Japanese media.
MALAYSIA: Two Malaysians being held, the government says.
IRELAND: A 36-year-old Irish man is among the hostages, according to the Irish government.
FRANCE: President Francois Hollande says there are French hostages but gave no exact number