"The attacks bear all the hallmarks of an al-Qaida attack," State Department spokesman Sean McCormack told reporters.

"At this point I am not prepared to draw some exact linkage for you but again if you look at the facts on the ground, it looks a lot like what we have seen in the past from al-Qaida," he said.

The White House also condemned the attack. "This attack is a reminder of the continuing threat we face from violent extremists both at home and abroad," US National Security Council spokesman Gordon Johndroe said.

"We will continue to work with the government of Yemen to increase our counter-terrorism activities to prevent more attacks from taking place," he said.

Earlier on Wednesday, an attack outside US embassy in Yemen resulted in the killing of six assailants, six soldiers and four civilians. No American personnel were killed and injured.

A radical group calling itself the Islamic Jihad in Yemen claimed responsibility for the attack.

Recent years have witnessed a string of terror attacks by Islamic militants in Yemen where al-Qaida leader Osama bin Laden was reportedly born.