Bombers and gunmen attacked policemen and a wake in Iraq among other targets, killing at least 44 people across the country on Thursday, in the latest burst of violence that has raised concerns about a return to civil strife.

Gunmen opened fire on two checkpoints guarding oil installations on the road between Haditha and Baiji, 180 km north of the capital, killing 11 people, police said.

In the town of Muqdadiya, 80 km northeast of Baghdad, a further 11 people were killed when a car bomb exploded at a wake. As survivors gathered to evacuate the wounded, a suicide bomber blew himself up, police said.

"I was sitting inside the tent...when I heard a huge explosion. I rushed out (and) saw a car burning. While we were busy evacuating the injured, a suicide bomber took us by surprise," said 47-year-old teacher Kadhim Hassan, who was taken to hospital with injuries to his leg.

The violence is part of a sustained campaign of militant attacks since the start of the year that has prompted warnings of wider conflict in a country where ethnic Kurds, Shi'ite and Sunni Muslims have yet to find a stable power-sharing compromise.

In eastern Baghdad, a car bomb killed four people, police and hospital sources said.

Three roadside bombs targeted police patrols in the city of Tikrit, killing three policemen. In the northern city of Mosul, three suicide car bombs targeted checkpoints killing four policemen, police said.

Earlier in the day, seven policemen were killed in attacks in the western province of Anbar, Iraq's Sunni heartland.

Insurgents have been recruiting from Iraq's Sunni minority, which resents Shi'ite domination since the U.S.-led invasion that toppled Saddam Hussein in 2003.

Sectarian tensions have been inflamed by the civil war in neighboring Syria, which is fast spreading into a region-wide proxy war, drawing in Shi'ite and Sunni fighters from Iraq and beyond to fight on opposite sides of the conflict.

Around 60 km southwest of the ethnically mixed city of Kirkuk, gunmen attacked a checkpoint, killing three members of a government-backed Sunni militia known as Sahwa. In Kirkuk itself, a roadside bomb killed a fourth Sahwa member.

The number of people killed in militant attacks across Iraq in June was 761, according to the United Nations. Violence is still well below the height of sectarian bloodletting in 2006-07, when the monthly death toll sometimes exceeded 3,000.-Reuters