Iraqi hospital officials say clashes have broken out in Sadr City, killing 11 men and wounding 19.
The clashes came even though Iraq's main Shiite political bloc and supporters of firebrand cleric Muqtada al-Sadr have signed a fragile cease-fire covering the Baghdad slum.
There has been sporadic fighting since the four-day cease-fire went into effect on Sunday.
Hospital officials say clashes erupted late yesterday and intensified early today. It was not immediately clear if the killed and wounded were militants or civilians. The officials spoke on condition of anonymity because they were not authorised to talk to the media.
Meanwhile, the US military says an attack helicopter came under fire Saturday by a surface-to-air missile over Sadr City but escaped the attack.