Three car bombs, including a suicide attack, a mortar round and a shooting killed at least seven people Sunday, most of them in northern Iraq where analysts fear tensions could trigger all-out conflict.

The deadliest attacks struck within territory which Iraqi Kurdistan wants to incorporate into its three-province autonomous region in spite of objections from Baghdad.

Diplomats cite the unresolved row as one of the biggest threats to the country's long-term stability.

In the town of Riyadh, just west of the ethnically mixed city of Kirkuk, three policemen were killed and 14 people were wounded when a suicide attacker set off a minibus rigged with explosives outside the police headquarters, police Brigadier General Sarhad Qader said.

Among the wounded in the morning attack were nine policemen, including local police chief Major Mundher Ahmed.

Another person was killed and 27 were wounded by two car bombs targeting Shiite Turkmen areas of Tuz Khurmatu, another ethnically diverse town in the disputed territory which stretches from Iraq's eastern border with Iran to its western frontier with Syria.

The row is one of several between the central government and the autonomous Kurdish region, and diplomats and analysts often voice worry that tensions tied to the disputes could spill over into armed conflict.

In central Baghdad, meanwhile, a mortar round hit the Allawi neighbourhood, killing two people and wounding five, officials said. And an off-duty soldier was gunned down by militants while he was in a barbershop in the main northern city of Mosul.

Iraq has suffered a surge in violence since the beginning of the year, coinciding with rising discontent among Sunnis that erupted into protests in late December.

Analysts say a failure by the Shiite-led authorities to address the underlying causes of the demonstrations has given militant groups both a recruitment platform and room to manoeuvre.