US warplanes have dropped bombs on east Baghdad district of Sadr City where hundreds of civilians have already been killed in air strikes.

Residents said low flying jets dropped bombs in sectors 22 and 24 of Sadr City, around midnight (2100 GMT Sunday).

About two hours later, according to witnesses, helicopters fired missiles at four targets in Sadr City.

The populated slum area has frequently been pounded by US aircraft or artillery. Many civilians have been killed and wounded as a result of the attacks.