Sana'a, Yemen - Six policemen and six suspected al-Qaeda attackers were killed in a car-bomb attack outside the US embassy in the Yemeni capital Sana'a Wednesday, witnesses and medics said.

Witnesses told Deutsche Presse-Agentur dpa that a car carrying armed men in police uniforms fired an RPG shell and drove into a road block around 100 metres outside the embassy's compound followed by another car loaded with explosives.

They said the second car exploded near the compound's main gate, sending smoke billowing over the area.

Residents said heavy gunfire followed the two blasts.

The men in the first car then clashed with security forces guarding the fortified compound that also hosts the ambassador's residence.

Three out of the 16 injured are policemen.

At least 13 people, mostly women and children in houses close the embassy, were injured and taken to two hospitals, they said.

Police officers at the scene said no embassy staff were hurt in attack.

Security forces cordoned off the area and prevented journalists from reaching the scene.

In a grenade attack carried out by extremists in front of the US embassy in March 2007, one Yemeni police officer was killed.

Three police officers and four girls in a neighbouring school were injured.

Al-Qaeda terrorists attacked USS Cole in the Gulf of Aden in 2000, killing 17 marines. dpa