Britain and the United States promptly closed their embassies in Yemen on Sunday after threats from an Al-Qaeda offshoot, while vowing to fight Yemeni extremists linked to a failed US airliner bombing.
A Yemeni government official earlier told AFP the British embassy was closed "for security reasons, and out of fear of possible Al-Qaeda reactions." But he stressed there were "no direct Al-Qaeda threats."
US President Barack Obama on Saturday accused the Yemen-based Al-Qaeda in the Arabian Peninsula, or AQAP, of arming and training a Nigerian suspect who targetted a Detroit-bound Northwest Airlines jet on Christmas Day.
AQAP claimed responsibility for the foiled attack and called for strikes on embassies in Yemen.
"There are indications that Al-Qaeda is planning to carry out an attack against (a) target inside of Sanaa, possibly our embassy," US Homeland Security and Counterterrorism Adviser John Brennan said Sunday.
Earlier the US embassy posted a statement on its website saying the closure was "in response to ongoing threats by Al-Qaeda in the Arabian Peninsula... to attack American interests in Yemen."
Fears grew after AQAP urged Muslims on Monday to conduct an "all out war" against Western targets in the impoverished Arabian Peninsula country.
"We call upon every Muslim who cares about his religion and doctrine to assist in expelling the apostasies from the Arabian Peninsula, by killing every crusader who works at their embassies or other places, declare it an all-out war against every crusader on Mohammad's peninsula on land, air and sea," it said in a statement.
London and Washington meanwhile agreed to fund Yemen's special Counter-Terrorism Unit -- a special force which in the past has received US training and assistance.
Brennan described the move as a "determined and concerted effort" but stressed Washington will not open up a new front in Yemen by sending in troops to help the authorities battle Islamist militants.
"We're not going to let Al-Qaeda continue to make gains in Yemen because we need to take whatever steps necessary to protect our citizens there as well as abroad," he told Fox News.
He also hailed the Yemeni government for making "real progress" against Al-Qaeda and said Washington was "providing everything they've asked for."
"In the past month, Al-Qaeda has take a number of hits. A number of Al-Qaeda leaders in Yemen are no longer with us," Brennan said.
Yemeni forces launched raids on suspected Al-Qaeda targets on December 17 and 24, killing more than 60 Islamist militants. A defence ministry newspaper said a plot to bomb the British embassy was also foiled.
Britain is due to host an international meeting on combating extremism in Yemen on January 28.
Yemen -- the ancestral homeland of Al-Qaeda chief Osama bin Laden -- is grappling with insurgents in the north and the south and has been rocked by several deadly anti-Western attacks.
Nineteen people were killed in a car bomb attack outside the US embassy in September 2008. In October 2000, 17 US military personnel were killed in a Al-Qaeda suicide attack on the USS Cole destroyer in southern Yemen.
The government has welcomed US and British help to fight extremism.
"Any assistance provided to Yemen's counter-terrorism force will be most welcome," a government official told AFP.
Source: AFP European Edition