A double suicide car bombing in central Baghdad has killed at least 15 people, the Iraqi interior ministry said.
The blasts hit a busy neighbourhood during rush hour
The cars blew up nearly simultaneously amid heavy traffic in a street near a fortified interior ministry office.
Police officers and several children were among the dead, witnesses said. More than 30 people were wounded.
Iraq has witnessed 18 months of bombings, shootings and kidnappings perpetrated by insurgents opposed to the US-led occupation of the country.
A statement on an Islamist website claimed that al-Qaeda in Iraq, headed by Jordanian militant Abu Musab Zarqawi, carried out the attacks. The claim could not be independently verified.
American and Iraqi officials had reported something of a downturn in insurgent attacks over the past couple of months.
But the BBC correspondent in Baghdad, Jim Muir, says the impression in recent days is that the tempo may be starting to pick up once again.
Third explosive device
Two huge explosions just a few seconds apart shook buildings all over the city and sent columns of black smoke pouring up into the sky.
US forces backed by helicopters moved in to secure the area and drive people back.
The Associated Press reports that American forces detonated a third explosive device near the scene.
An interior ministry source is quoted as saying the bombers blew themselves up as a convoy of seven police vehicles drove through the busy Jadriya neighbourhood.
One police officer who spoke to journalists was travelling in the convoy that was targeted.
"We were cutting through the traffic jam when a car in the middle of the crowded street blew up. We crossed over to the other side...and another car tried to cross, but it flipped over and when it did it also blew up," the officer said.
In other violence on Thursday, three policemen and a civilian were killed in a drive-by shooting at a police station in the northern city of Kirkuk.
There are also reports of attacks on Iraqi police and the US military in Baquba and Tikrit, north of Baghdad.
One Iraqi officer died in the attack on a police patrol near Baquba, while a car bomb reportedly exploded outside a US military installation in Tikrit, injuring nine civilians.