Five bombs exploded at a northern Iraqi oil field on Saturday morning, damaging two pipelines without affecting the country's vital crude exports, officials said.

The pipelines transport oil from the Bai Hassan field in the disputed province of Kirkuk to the Ceyhan pipeline that exports crude via Turkey.

Iraq detained 22 policemen on Saturday after 19 inmates, including two men on death row, escaped from a prison in the northern city of Kirkuk a day earlier, the local police chief said.

"We are investigating 22 policemen who have been detained, to find out about the escape of the terrorists," Kirkuk provincial police chief Jamal Taher Bakr told AFP, adding that local police were hunting for those on the run.

Iraq's autonomous Kurdistan region halted crude exports on Sunday, nearly a week after it rejected a new oil and gas law approved by the central government, Oil Minister Abdelkarim al-Luaybi said.

"The government of the Kurdistan region today halted oil exports without giving reasons," Luaybi told Agence France Presse on the sidelines of an oil conference in the Jordanian capital.

At least 25 people, all but one of them women and children, were killed when a bus caught fire after being hit by a car in the northern Iraqi city of Kirkuk on Saturday, a police chief said.

The families were travelling on the bus from Baghdad to the northern Kurdish province of Dohuk when the vehicle got stuck in a pothole, according to Kirkuk province police chief Major General Jamal Taher Bakr.

An al-Qaida militant has been killed together with his two children when a car bomb he was making at his home exploded near the northern Iraq city of Kirkuk, police said on Tuesday.

"An al-Qaida terrorist, Mohammed Nussayef Jasim al-Hamdani, was killed while trying to fit a bomb inside a vehicle at his home," a police official in Kirkuk said.

A spate of bomb attacks against police in the disputed northern oil-rich city of Kirkuk on Thursday killed at least 27 people, the worst violence to hit Iraq in nearly two months.

A further 89 people were wounded in the three attacks; with just months to go before U.S. forces must withdraw from the country.

A Christian man in the northern Iraqi city of Kirkuk has been kidnapped and is being held for a $100,000 ransom, police said Saturday.

Kirkuk deputy police chief Maj. Gen. Torhan Abdul-Rahman said the victim is a construction worker who did not come home from work Friday night. When officials called his mobile phone on Saturday, the kidnappers answered and demanded the money.