BBC News - Yemen says it has foiled an al-Qaeda plot Yemen says it has foiled an al-Qaeda plot to blow up oil pipelines and seize some of the country's main ports. Security remains tight and hundreds of armoured vehicles have been deployed to protect key sites. Both the US and UK have withdrawn diplomatic staff from Yemen, prompted by intelligence reports of renewed terrorist activity. The US is reported to be preparing special operations forces for possible strikes against al-Qaeda in Yemen. Suspected US drone strikes killed seven alleged al-Qaeda militants in Yemen on Wednesday - the fifth such strikes in less than two weeks. The drones also destroyed two vehicles in the town of Nasab, in the southern province of Shabwa. Audacious plot The threat picture in Yemen grows ever murkier. First came the hurried withdrawal of nearly all the Western diplomatic corps from the country on Tuesday, prompted by fears of a major al-Qaeda attack against US or Western embassies and their staff. Now the Yemeni authorities have announced what appears to be a separate plot by al-Qaeda to target Yemen's own government installations, including ports, pipelines and the military. The hard part is distinguishing this from the ongoing, underlying threat from all-Qaeda and other militants that exists anyway, throughout the year. Yemen has long been troubled by disgruntled tribesmen blowing up pipelines that run through their territory, or kidnapping foreigners to pressure the government for economic concessions. But since the Arab Spring upheavals, al-Qaeda in Yemen has profited from a security vacuum in remoter provinces and continues to try to stage spectacular attacks. Yemeni government spokesman Rajeh Badi said the plot involved blowing up oil pipelines and taking control of certain cities - including two ports in the south, one of which accounts for the bulk of Yemen's oil exports and is where a number of foreign workers are employed. "There were attempts to control key cities in Yemen like Mukala and Bawzeer," said Mr Badi. This would be co-ordinated with attacks by al-Qaeda members on the gas facilities in Shebwa city and the blowing up of the gas pipe in Belhaf city. Al-Qaeda members dressed as soldiers were to be outside the ports, he said. On a given signal they were to invade the facility and take it over. Yemeni officials quoted by AP news agency said they believed the motive for the planned attacks was retaliation for the killing of senior al-Qaeda figure Said al-Shihri, who was critically wounded in a November drone strike and later died of his injuries. Security blitz The BBC's Abdullah Ghorab, in Sanaa, says there are unprecedented security measures in the capital, with hundreds of armoured vehicles deployed around the city. Tanks and troops have surrounded foreign missions, government offices and the airport, and senior officials are being advised to limit their movements. A human rights advocate in Sanaa, Samia Haddad, told the BBC's World Update programme that the atmosphere in the city was tense. "Everybody is feeling that there is something going on, but nobody knows what is going on exactly," she said. The US embassy and consulate closures reportedly followed intercepted conversations between two senior al-Qaeda figures, including top leader Ayman al-Zawahiri, suggesting terrorist attacks. The Yemeni government spokesman said the international community "feared the reaction of al-Qaeda" and added: "We understand such fears." But the foreign ministry has criticised the embassy withdrawals, saying it "serves the interests of the extremists." US special forces Sources have told BBC Newsnight that the US is preparing special operations forces for possible strike operations against al-Qaeda in Yemen. Yemen is the base of al-Qaeda in the Arabian Peninsula (AQAP) and both the White House and the US state department have said the current threat comes from AQAP but have refused to divulge further details.