BAGHDAD, Sep 25 (Reuters) - U.S. troops clashed with militia fighters loyal to a rebellious Shi'ite Muslim cleric in eastern Baghdad on Sunday, killing eight militiamen and wounding five, Iraqi police said. They said U.S. forces entered the poor Shi'ite district of Sadr City seeking to detain a group of militia members suspected of carrying out guerrilla attacks. The militia, known as the Mehdi Army, is loyal to Moqtada al-Sadr, a young radical cleric whose followers have led two uprisings against U.S. forces. The U.S. military said it had engaged what it termed anti-Iraqi forces in several locations in...