A close aide to Shi'ite cleric Moqtada al-Sadr's ordered his Mehdi Army militiamen on Thursday to observe a ceasefire after they clashed with Iraqi and U.S. soldiers in the southern city of Kut.
Sadr, whose militia fought two battles against U.S. forces in southern Iraq in 2004, extended a seven-month-old ceasefire last month, but at the weekend issued a statement telling followers they could defend themselves if attacked.
The violence in Kut, 170 km (105 miles) southeast of Baghdad, raised fears that the ceasefire was unravelling.
"We call on them to calm down and to cease fire and to stop shedding the blood of Iraqis, this is the opinion of Sadr, whether it is in Kut or any other Iraqi provinces," aide Luwaa Sumaisem told Reuters in the holy city of Najaf.
Since January, violence in Iraq has increased.
The body of Paulos Faraj Rahho, the Chaldean Catholic archbishop of Mosul who was kidnapped last month, was found dumped in the northern city on Thursday, police said. It was not clear how he had died, they said.
At least 12 people were killed and 49 wounded when a bomb exploded in a parked car in the busy shopping district of Bab al-Sharji in central Baghdad on Thursday, police said.
Militia fighters in Kut battled Iraqi and U.S. forces on Tuesday in day-long clashes that police said killed 11 people, and late on Wednesday night gunmen in a neighbourhood with a strong Mehdi Army presence fired rockets at a nearby U.S. base.
A police official said as many as 11 Katyusha rockets landed on the U.S. base. Residents said the attackers were Mehdi Army.
Two brothers were killed and four other people, including a 6-year-old girl, were wounded when U.S. soldiers responded with mortar rounds, the police official said.
A U.S. military spokeswoman said troops had responded after four rockets were fired at the base. She had no information on civilian casualties but said no U.S. soldiers had been hurt.
