Smoke rises over buildings in Sanaa, after a car bomber and gunmen dressed in army uniforms attacked Yemen's Defence Ministry compound, targeting the hospital.

Sources say the attack began as ministry employees were arriving for work, when a vehicle exploded at the compound's gate.

At least 20 people were reported killed, and dozens wounded.

Ambulance sirens and gunshots were heard after the blast, as security forces exchanged fire with the gunmen. The Ministry said most of the gunmen had been killed or wounded.

Witnesses at the scene describe the attack.

(SOUNDBITE) (Arabic) UNIDENTIFIED WITNESS, SAYING:

"We first heard the sound of gunfire then we realized that there were people dressed in military uniforms throwing bombs inside the hospital."

(SOUNDBITE) (Arabic) UNIDENTIFIED WITNESS, SAYING:

"We heard the sound of the explosion, it hit the neighborhood and broke the windows of the houses, people and children were terrified."

Yem