At least 10 police volunteers have been killed and more than 20 others injured in an explosion in central Baquba, Iraqi police sources said.

The attack occurred in Baquba, 50km north of Baghdad, on Tuesday where the Iraqis were submitting applications to join Iraq's Quick Reaction Police Force, said a police commander who spoke on condition of anonymity because of concerns about his security.

Monday's blast - set off by explosives hidden under the bomber's clothing - occurred inside a police building where the applications were being filled out and accepted, the commander said.

Iraqi journalist Husain al-Azzawi told Aljazeera quoting Iraqi police sources that a bomber wearing a belt of explosives blew himself up at 10am on Tuesday among a crowd of Iraqi police volunteers.

Other sources reported that the explosion was caused by a mortar shell that landed among the crowd of volunteers, al-Azzawi said but cast doubt on the veracity of this account.

He said the number of casualties is expected to rise as a large number of volunteers had gathered at the police station at the time of the attack.

The Baquba office of Iraq's Quick Reaction Police Force has previously come under attack several times, al-Azzawi said.

Iraqis killed in Ramadi

In other developments, three Iraqis were killed by US firing in Ramadi, Aljazeera reported quoting Iraqi medical sources. The incident took place after a US patrol came under a bomb attack which destroyed an armoured troop carrier.

In western Ramadi, an Iraqi was killed and four others were injured when US bombs fell on a market in al-Ubaidi area. The attack also damaged many shops, Iraqi police sources told Aljazeera.

PHOTO CAPTION

Iraqi police examines the remains of a car following a car bomb attack in Baghdad, Iraq, Tuesday Sept. 27 2005. (AP)