From the New York Times:
Baghdad Mayor Is Ousted by a Shiite Group and Replaced
BAGHDAD, Iraq, Aug. 9 - Armed men entered Baghdad's municipal building during a blinding dust storm on Monday, deposed the city's mayor and installed a member of Iraq's most powerful Shiite militia
This is the new Iraq," said Mr. Tamimi, a secular engineer with no party affiliation. "They use force to achieve their goal."
The group that ousted him insisted that it had the authority to assume control of Iraq's capital city and that Mr. Tamimi was in no danger. The man the group installed, Hussein al-Tahaan, is a member of the Badr Organization, the armed militia of the Supreme Council for Islamic Revolution in Iraq, known as Sciri.
The militia has been credited with keeping the peace in heavily Shiite areas in southern Iraq but also accused of abuses like forcing women to wear the veils demanded by conservative Shiite religious law.