BAGHDAD �American military forces for the first time conducted air strikes on targets in Basra late Thursday, joining Iraqi security forces in trying to oust Shiite militias in the southern port city.

Shiite militiamen cover an area during a gun battle with government forces in Basra on Friday.

Two American war planes shelled two separate targets in Basra, entering the battle at the request of the Iraqi Army, which asked the American and British forces to strike two militia targets in the city, according to Maj. Tom Holloway, a spokesman for the British Army in Basra.

The air strikes are the clearest sign yet that the coalition forces are becoming involved in the fighting in Basra. Up until Thursday night, the American and British air forces had been working in cooperation to provide surveillance support for the Iraqi Army.