A suicide bomber has crashed his car into a barrier outside a police building in central Iraq, killing at least 13 people and wounding dozens more, officials said.

The blast is the second significant attack in Iraq since the death of Osama bin Laden on Monday at the hands of a US commando team in Pakistan.

Iraqis have been on edge, waiting for al Qaida's branch in Iraq to strike back.

Security officials say they are increasing security in the wake of bin Laden's killing.

A police official said the bomber hit when the police were changing shifts in the city of Hillah, about 95 kilometres south of the capital Baghdad.

Most of the dead and wounded were police, he said.

The official put the number of dead at 13 and said 41 people were wounded.

Hillah is a predominantly Shiite city but its proximity to the Triangle of Death - a mainly Sunni area that at one time was one of the most dangerous in the country - has made it a frequent target of Sunni extremists.

There was no immediate claim of responsibility for today's blast.

On Tuesday, a car bomb tore through a cafe in a Shiite enclave in Baghdad packed with young men watching a football match on TV, killing at least 16 people.