Six car bombs killed more than 150 people and wounded another 250 in the Shia suburb of Sadr City yesterday in the bloodiest attack in Baghdad since the US invasion began.
The blasts came at the same time as gunmen surrounded and fired on the Shia-run Health Ministry in one of the boldest daylight assaults by militants in Baghdad. Mortars later crashed down on a nearby Sunni enclave in an apparent reprisal attack.
Leaders from all main communities made a televised appeal for calm, a step last taken in February when the bombing of a major Shia shrine, blamed on al-Qaeda, launched a wave of bloodshed that has gathered force in the past nine months.
"We call on people to act responsibly and to stand together to calm the situation," the statement read.
In Sadr City, parked vehicles packed with explosives caused carnage in streets and a market, a police general told state television.
Mortars also landed nearby and residents seized a seventh car which they said was driven by a would-be suicide bomber.
"As the bombs went off, everyone started running and shouting," news photographer Kareem al-Rubaie said. "I saw a car from a wedding party, covered in ribbons and flowers. It was burning. There were pools of blood . . . and children dead."
Heavily guarded and policed by the Mehdi Army militia of radical Shia cleric Moqtada al-Sadr, Sadr City was until this year relatively unscathed by al-Qaeda and other Sunni insurgent attacks.
A string of bombings against civilians there in recent months is seen as a declaration of war on the militia, which Sunnis blame for much of this year's death squad violence.
The bloodshed may heighten sectarian anger after a week of tension inside the US-backed national unity government.
Washington is pressing Shia and minority Sunni leaders to rein in militants to halt a slide towards all-out civil war.
Noting that yesterday was the seventh anniversary - by the Islamic calendar - of the killing of Sadr's father by Saddam Hussein's agents, Sadr ally Fattah al-Sheikh blamed "terrorist groups and Saddamists" as well as the US occupation.
He vowed: "Sadr City will be the rock on which all conspiracies will founder."
Another Shia figure, Sami al-Askari, demanded the arrest of a top Sunni politician for inciting sectarian violence.
Five people were wounded at the health ministry, about 5km from Sadr City, an interior ministry source said, when guerrillas fired mortars, rocket-propelled grenades and machine guns into the compound.
The arrival of US helicopters and troops dispersed the assailants, ministry employees said. The Health Ministry is run by followers of Sadr. The US military said it was unaware of any such attack.
Shortly afterwards, mortar rounds hit Adhamiya, an enclave of Iraq's Sunni minority in mainly Shia east Baghdad.
The Interior Ministry said 10 people were wounded in the attack. A local resident said he heard more than 20 mortars hit the area, one damaging the renowned Abu Hanifa Sunni mosque.