At least 14 people have been killed and 30 others injured in a string of attacks across Iraq, with the worst targeting a police headquarters near Baquba, officials say.

A suicide bomber rammed an explosives-laden truck into a concrete blast wall outside the building in the town of al-Salam on Wednesday morning, a police officer said. At least seven people were killed and 14 others wounded in that attack.

The town is about 75km northeast of the capital Baghdad and close to the city of Baquba, a former al-Qaeda stronghold that has experienced scores of attacks during a nationwide spike in violence in the last few months.

A separate bombing in an outdoor market in Baghdad's northern Sab al-Bor suburb killed four and wounded 13. A sniper also killed a policeman at a checkpoint in the capital's eastern Sadr City, police said.

In Baghdad's western suburb of Abu Ghraib, a bomb hit a patrol of a pro-government, anti-al-Qaeda militia, killing two and wounding three others, a police officer said.

The Sunni group, known as the Awakening Council, was formed by US forces in late 2007 to help fight fighters.

Medical and police officials confirmed the causality figures. All officials spoke on condition of anonymity as they were not authorised to talk to the media.

Violence has spiked in Iraq since April, with the pace of killing reaching levels unseen since 2008.

Today's attacks bring the death toll across the country this month to at least 46, according to a tally by the Associated Press news agency.

According to UN figures, more than 5,500 people have been killed since April.

Source: Agencies