The U.S. military says 18 Shi'ite militants have been killed in fierce battles with U.S. troops in western Baghdad.

The military says the fighting erupted early Friday after militants fired on a U.S. patrol in Baghdad's Shula district.  The military says U.S. attack helicopters fired on up to a dozen militants who had assault rifles and rocket-propelled grenades.

The area is known to be a stronghold of the Mahdi Army militia that is loyal to radical Shi'ite cleric Moqtada al-Sadr.  Witnesses say there were civilian casualties.

In other news, a U.S. commander in Iraq says he is troubled by the scale of support members of the Iranian Revolutionary Guards are allegedly providing to insurgents in Iraq. 

Army Major General Rick Lynch, commander of troops south of Baghdad, says there are an estimated 50 Iranian and Iraqi operatives working for Iran in his region alone.     

The general, speaking to Pentagon reporters in a video conference, says Iranian forces are facilitating training and providing weapons and munitions to insurgents.  Iran has denied it is providing military support to Iraqi insurgents.

Separately, the military says a U.S. soldier was killed and four others wounded in an explosion Friday in Salah-ad-Din province north of Baghdad.

Also, the U.S. military says coalition forces have killed 12 insurgents in various raids, including in an operation today in Baghdad targeting car bomb networks.

In other news, Iraqi Vice President Tareq al-Hashemi says his Sunni political party, the Iraqi Accordance Front, will not return to the Cabinet unless its demands for reform are met.  He spoke from Turkey today.

Some information for this report was provided by AFP, AP and Reuters.