A car bomb has killed 10 people and wounded 21 near a vegetable market in Baghdad, Iraqi police say, as insurgents kept up a campaign of bombings despite a new US-backed security crackdown.

Police say the bomb went off along a commercial street in the Bayaa neighbourhood of the Iraqi capital.

US and Iraqi forces launched a crackdown in Baghdad two weeks ago, but bombings and other attacks persisted.

American commanders have urged patience, saying it will take time for the offensive against militants to have a lasting impact.

A report of a bomb on Tuesday that killed 18 people, mostly children, in the Iraqi city of Ramadi was wrong and stemmed from confusion over a similar attack the day before, police officials and residents say.

The reported killing of so many children had drawn swift condemnation from the President and the Prime Minister, but Colonel Tariq al Theibani, security adviser for Anbar province, says the report of the bombing on Tuesday was wrong.

"It happened the day before yesterday," he told Reuters.

He said 18 people, many of them children, were killed on Monday by a suicide car bomb, as previously reported.

The US military had put the death toll from that attack at 15.

Iraq's government and police had reported another bomb near a soccer field killing 18 people, mostly children.

The US military, which has a heavy presence in Anbar, had said it was unaware of such an attack.

The US military says it carried out a controlled explosion in the western city, also near a soccer field, that wounded 30 people, including nine children on Tuesday afternoon.

Colonel Theibani says the confusion may have arisen partly because the victims of Monday's car bomb were buried on Tuesday.

The loud blast from the controlled explosion near a soccer field may have also contributed to the confusion.

Colonel Theibani blamed Monday's attack on Al Qaeda, saying it was part of a campaign against tribal leaders and communities that have taken a stand against the insurgent group in Anbar.

- Reuters