Baghdad: A rocket hit a downtown Baghdad park on Thursday, killing two civilians even as US-backed forces tried to weaken Shiite extremists and disrupt rocket and mortar strikes from the militia stronghold of Sadr City.

It was the second rocket that landed in a downtown park in three days, apparently after failing to reach the US-protected Green Zone, which includes the US Embassy and key Iraqi government offices.

US forces have increased air power and armoured patrols in an attempt to cripple Shiite militia influence in Sadr City, a slum of 2.5 million people that serves as the Baghdad base for the Mahdi Army led by anti-American cleric Moqtada Al Sadr. Seventeen fighters were killed in clashes since Wednesday, the military said on Thursday.

The rocket that landed in the park near the Al Sadoun street yesterday also wounded six civilians, police said.

Earlier yesterday, some residents in southeastern section of Sadr City claimed that Iraqi soldiers warned them to leave their houses and go to nearby soccer stadiums for security reasons. But the US military denied the claim and called it a "rumour."

Unicef says about 6,000 people have been forced to flee their homes in Sadr City, most of them from the southeastern section.