Al-Qaeda claimed responsibility Friday for a brazen attack on a Yemeni defence complex that killed 52 people, saying it targeted the site as it hosted US personnel behind drone strikes against its militants.
Al-Qaeda in the Arabian Peninsula (AQAP), regarded by Washington as the jihadist network's most dangerous affiliate, has been hit by intensified US drone strikes targeting its militants in Yemen this year.
But there was no immediate evidence to support its allegation that the Sanaa complex attacked on Thursday played any role in the drone war or housed any US personnel.
All of the dead came in a hospital inside the sprawling facility which bore the brunt of the armed assault that came after a suicide bomber rammed a vehicle packed with explosives into the main gate.
The complex in central Sanaa was "stormed... after the mujahedeen (holy warriors) proved that it accommodates drone control rooms and American experts," AQAP said in a statement published by its media arm on Twitter.
"As part of a policy to target drone control rooms, the mujahedeen have dealt a heavy blow to one," it said.
"Such security headquarters in partnership with the Americans in their war on these Muslim people are a justified target wherever they may be."
Washington condemned the attack which cames as Defence Minister Mohammed Nasser headed a military delegation on a visit to the United States.
Deputy State Department spokeswoman Marie Harf said she had no information about any US casualties.
Two doctors from Germany, two from Vietnam and another from Yemen were killed, as well two female nurses from the Philippines and one from India, Yemen's official Saba news agency said.
But the Philippine foreign ministry gave a higher death toll for its nationals, saying that seven had died, all medical staff and including a doctor.
The remaining "martyrs" were all patients in the hospital, including both soldiers and civilians, among them a top Yemeni judge and his wife, Yemen's supreme security committee said.
The defence ministry said gunmen occupied the hospital after the explosion, but that security forces had regained control of the building.
But residents in Sanaa said the sounds of clashes and explosions rang out from the area and were heard across the capital throughout the night until fighting subsided at dawn on Friday.
The area was cordoned off in the morning while armoured vehicles blocked all roads leading to the defence complex, witnesses said.
A search was mounted for two suspected bomb-laden vehicles the militants were planning to use in more attacks, said security officials, who added that up to 25 militants had carried Thursday's assault.
The brazen daylight attack on the complex followed a spate of hit-and-run strikes on military personnel and officials, as Yemen struggles to complete a thorny political transition.
The attacks have mostly generally been blamed on AQAP, which remains very active despite suffering setbacks in a major army offensive in the south last year and repeated US drone strikes on its commanders.
AQAP has been linked to several attempted attacks on the United States, including a botched bid to blow up a Detroit-bound airliner on Christmas Day in 2009, which have made it a major target of the US "war on terror".
The number of dead from US drone strikes in Yemen remains unclear and estimates vary widely.
According to the New America Foundation, a Washington-based think-tank that has tried to keep track of the numbers, there have been 93 strikes since 2002 which have killed between 684 and 891 people, among them between 64 and 66 civilians.
According to a Human Rights Watch report published in October, the US has carried out 80 targeted operations in Yemen since 2009, including strikes from drones, warplanes and cruise missiles -- killing at least 473 people.
US President Barack Obama has defended the drone bombing campaign as an effective tool against Al-Qaeda, but has promised to introduce stricter rules and oversight for the strikes, including shifting more of the operations from the CIA to the military to reduce secrecy.