Early reports had cited at least 25 and as many as 45 policemen killed and many others injured.

However, Major-general Walid Khalid Abd al-Salam, head of the Diyala provincial police, said there had been no deaths.

Speaking to Aljazeera, Abd al-Salam said two policemen were injured and two vehicles damaged. There were no deaths among the policemen, he said, but up to seven of the assailants were killed.

"No policemen have been killed. The reports are false," said Abd al-Salam.

The attacks occurred about 7am (0400 GMT) at police stations in the towns of Buhriz and Mufraq, 57km north of Baghdad.

Abd al-Salam said three of the attackers were killed in Buhriz while four others were killed in the attack in Mufraq. 

In Mufraq, the bodies of the dead  were taken by their fellow assailants.

Residents reported seeing US helicopters flying over the area and explosions of gunfire.

Kirkuk explosion

Elsewhere, a car bomber killed himself and two Iraqis in an explosion outside an Iraqi National Guard base near the northern city of Kirkuk on Tuesday, police said.

More than a dozen policemen 
have been killed recently 

Three other people were injured in the attack which occurred in Kiwan, about 20km north-west of Kirkuk, an ING spokesman said.

Iraq's National Guard and its police force are a constant target for attacks by fighters opposed to the US-backed interim government.
 
In the past few days, fighters have killed tens of policemen in a series of coordinated strikes.
 

Baghdad blast

Four mortar explosions rang out in Baghdad on Tuesday and smoke rose from near the heavily fortified Green Zone compound, witnesses said.

The blasts occurred as US helicopters were coming in to land in the sprawling complex that is home to key Iraqi government offices and the US and British embassies.

Black whisps of smoke could be seen rising in the centre of the city, about one kilometre away from the Green Zone, indicating the point from where the mortars were fired.

On Monday, a series of car bomb attacks targeted a church, a hospital and a convoy travelling on the road to Baghdad's airport, a strip that has become notoriously dangerous. 

Aljazeera has also learned that clashes erupted on Tuesday between US forces and armed men in al-Qaim city, near the Iraqi-Syrian borders. Two children were killed and five other civilians injured.