(updates with 11 more killed on Friday)

BAGHDAD, May 9 (Reuters) - U.S. forces have killed 25 militants in the past two days in the Baghdad slum Sadr City, a stronghold of anti-American Shi'ite cleric Moqtada al-Sadr, the military said on Friday.

The gunmen were killed in several clashes on Thursday and Firday, the military said in a series of statements. It said air strikes and tanks were used to attack militiamen trying to launch rockets from the slum or shoot at U.S. troops on patrol.

Hospitals in Sadr City said they had received four bodies and treated 51 wounded by Friday morning, but gave no further casualty figures after that. Among the wounded were children.

In one operation, U.S. special forces killed 11 special groups fighters -- a term the military uses for Shi'ite armed groups it says receive weapons and training from Iran -- after they attacked a joint U.S. and Iraqi military patrol.

Fighting has raged in Baghdad since Prime Minister Nuri al-Maliki ordered a crackdown on militias in late March.

Several hundred people have been killed in fighting that shows no sign of easing. Aid workers have warned of a looming humanitarian crisis in Sadr City, home to 2 million people.

Maliki, himself a Shi'ite, says the crackdown aims to disarm militias but Sadr's followers see it as an attempt by the U.S.-backed government to sideline the cleric's mass movement before local elections in October.

Sadr, who has a strong following among dispossessed Shi'ites, threatened last month to scrap a truce he imposed on his Mehdi Army in August. A few weeks later he urged his men to observe it, leaving many confused about his true intentions. (Reporting by Tim Cocks, editing by Tim Pearce)

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