At least 13 people have been killed in a shootout between prisoners and policemen at a police station in Iraq.

Seven suspected al-Qaeda fighters and six policemen were killed at the al-Fursan police station in Ramadi on Friday, Tariq al-Dulaimi, the police commander for Anbar province, said.

"During an exchange of fire between prisoners trying to escape and police officers in the station, six policemen and seven prisoners were killed," al-Dulaimi said.

Three fighters from the Islamic State in Iraq group, which is linked to al-Qaeda, fled captivity with one later re-arrested.

Al-Dulaimi said that police were going from house to house with photos of the fugitives on Friday morning.

"The people of this city will help us bring them back to justice," he said.

Police imposed a curfew on the city which lies 100km west of Baghdad, the capital.

The breakout attempt is said to have begun at 2am (23:00GMT), when the suspects killed a policeman and stole his weapon, before clashing with other members of staff.

Ramadi is a predominately Sunni city which was an al-Qaeda bulwark after the 2003 US-led invasion of Iraq.

However, since 2006 Sunni tribes in the area have sided with the US military and al-Qaeda fighters pushed out of the region.