Mosul: A suicide bomber smashed a police base in northern Iraq and another blew up a patrol today, killing 20 people as a pro-government militia killed 15 suspected Al-Qaeda fighters, officials said.

The surge in violence came as the US military announced plans to withdraw 4,000 more troops after saying the level of violence was at a four-year low.

A man in an explosives-packed jacket blew himself up at police headquarters in Sinjar, a town on the road to Syria from the main northern city of Mosul. A hospital source said 17 people were killed and 30 wounded.

Interior ministry spokesman Major General Abdul Kareem Khalaf said the local police chief was suspended pending investigations.

The authorities in Nineveh province slapped a ban on cars without passengers in a move aimed at minimising the risk of suicide car bomb attacks which are usually launched by lone drivers.

The mountains around Sinjar are a major centre for Iraq s non-Muslim Yazidi Kurdish community and saw the single deadliest attack since the US-led invasion of 2003.

Last August, suicide bombers in lorries killed more than 400 people in two Yazidi villages near Sinjar.

Only hours before today s attack, a suicide bomber targeted a group of police officers in Al-Gabat, a northern neighbourhood of Mosul, police said.

At least three people, including two policemen, were killed and 12 people wounded.

In neighbouring Salaheddin province, a militia allied to US and government forces killed 15 suspected Al-Qaeda members at Tikrit, 180 kilometres north of Baghdad.

Members of the Sunni "Awakening" movement opened fire as the suspects tried to escape from the vehicle at a checkpoint, militia official Ahmed al-Dulaini said.

Source : PTI