McClatchy reports:

A cease-fire critical to the improved security situation in Iraq appeared to unravel Monday when a militia loyal to radical Shiite Muslim cleric Muqtada al Sadr began shutting down neighborhoods in west Baghdad and issuing demands of the central government.

Simultaneously, in the strategic southern port city of Basra, where Sadr's Mahdi militia is in control, the Iraqi government launched a crackdown in the face of warnings by Sadr's followers that they'll fight government forces if any Sadrists are detained. By 1 a.m. Arab satellite news channels reported clashes between the Mahdi Army and police in Basra.