On Saturday, two men in a car hurled the explosive at a Yemeni Air Defence Academy bus outside the building where the two Iraqis live in western Sanaa and sped away, witnesses told AFP.

The two Iraqi officers are trainers at the Yemeni Academy of Air Defence and Aviation, Aljazeera's bureau chief in Sanaa said.

The five wounded men were taken to the military hospital in Sanaa. Some had serious injuries, the witnesses and medical sources said.

A Yemeni official, who requested anonymity, told AFP that three Iraqi experts who teach at the air defence academy were among the wounded. They include an officer.

On 25 April, a student was killed when a man hurled a hand grenade at a Defence Ministry vehicle in the Yemeni capital, sparking a shootout with security forces in which the attacker was killed.

Yemen has in the past few years been the scene of attacks blamed on Sunni militants loyal to al-Qaida. More recently, government forces and rebels from the al-Zaidi minority have fought fierce battles in the northwestern mountains.

It was not immediately known whether Saturday's attack was the work of al-Zaidi insurgents. Authorities said on Thursday that they had arrested 11 members of the community suspected of carrying out attacks in the capital as part of an uprising against the government.