US troops captured a suspected "special groups" leader and three others in a raid south of Baghdad, the US military said Friday. The operation took place late Thursday in the Mashru area, the military said in a statement. The military uses the language "special groups" to describe Shiite Muslim militias allegedly backed by Iran. The US says the groups have broken ranks with Muqtada al-Sadr's Mahdi Army. The radical cleric in August called a six-month cease-fire, which is due to expire later this month.