At least five Yemeni soldiers were killed Sunday morning by presumed members of Al Qaeda in an attack on a military checkpoint in the province of Shabua in southern Yemen, an official with the security forces told Efe.

The attackers staged a surprise attack on the soldiers while the latter were sleeping beside the checkpoint in the Rodum zone, at the natural gas export port of Balhaf, 570 kilometers (353 miles) southeast of Sana'a.

The terrorists opened fire with machineguns on the soldiers, who belonged to a special brigade tasked with monitoring the country's oil and gas facilities, and then fled.

The military source did not rule out that the attack could have been staged in retribution for recent army operations against Al Qaeda militants, operations in which U.S. drones have been used.

Washington last Tuesday asked its citizens to leave Yemen immediately because of a serious terrorist threat in the country, while London temporarily withdrew all British personnel from its embassy in Sana'a.

The U.S. Embassy in Yemen remained closed on Sunday, in contrast to other U.S. diplomatic offices, which opened their doors after the alert declared a week ago by Washington.

The U.S. government had ordered about 20 of its diplomatic posts, mainly in the Mideast, temporarily closed to guard against what it said was a serious terrorist threat. EFE