Neighbourhood patrols, which are mainly Sunni and include many men who previously fought against the US-led forces, have been credited with helping to reduce violence. But they are increasingly under attack from al-Qaeda loyalists.

Among those killed were members of the tribal forces, guards of the oil company and civilians, including at least four children, the police officer said.

The interior minister ordered the dismissal and interrogation of Saad Nufous, Baiji's police chief, shortly after the attack.

"There was a decision by the interior minister to fire the Baiji police chief," a ministry spokesman said.

Baquba attack

In Baquba, a bomber blew himself up in the middle of a funeral procession, killing at least four people from a similar group fighting al-Qaeda, police and medics said.

  

A wounded fighter of the Brigades of 20th Revolution receives treatment at Baquba hospital [AFP]

The US military said 10 Iraqis were killed in total and five wounded in the attack.

A doctor from Baquba hospital confirmed the casualties.

Police Lieutenant-Colonel Najim al-Sumaidaie said the procession was marking the death of two members of the Brigades of 1920 Revolution who were killed on Monday by the US military.

"The two were killed by mistake and the funeral was being held today when the suicide bomber attacked," he said.

The latest bombings highlighted al-Qaeda's fight back against the mushrooming number of groups across Iraq that oppose it.

About 80,000 Sunni Arabs who were formerly opposed to the US military now fight alongside them. They have turned on al-Qaeda in several Sunni regions of the country.

Attacks have increased in northern Iraq after armed groups were pushed out of western and central regions following a series of military operations.

US and Iraqi forces are currently involved in a wide scale military sweep in the northern provinces of Salah al-Din, which includes Baiji, Nineveh and Kirkuk.