Two bombings in Iraq's disputed northern oil province of Kirkuk killed two policemen and two soldiers on Monday, the latest in a string of attacks in the region, security officials said.
The violence further raised tensions in Kirkuk, an ethnically-mixed province which Kurdish leaders want to incorporate in their northern autonomous region over the opposition of its Arab and Turkmen communities, in a dispute US officials have long said is one of the biggest threats to Iraq's stability.
A morning car bomb targeting the convoy of a police commander in Al-Rashad, south of Kirkuk city, killed two policemen and wounded 12 other people, an officer said.
Major Ahmed al-Barzanji and four other policemen were among the wounded.
On the road to Kirkuk from Tuz Khurmatu further south, a roadside bomb targeting a patrol in the early hours killed a captain and another soldier, the town's police chief, Colonel Ali Hamdani, said. Two more soldiers were wounded.
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On Saturday, seven people were killed in attacks in Kirkuk province, two days after three bombings in the provincial capital killed 29 people in Iraq's deadliest day since late March.
Currently, US forces participate in confidence-building tripartite patrols and checkpoints with central government forces and Kurdish security officers in Kirkuk and across northern Iraq.
But the withdrawal of some 45,000 US troops still in Iraq must be completed by the end of the year, according to the terms of a bilateral security pact.
And in Baghdad, a car bomb blew up in the eastern Zayouna neighbourhood at around 4:00 am (0100 GMT), destroying 13 shops, including seven alcohol stores, an interior ministry official said.
There were no casualties resulting from the attack, the official said, speaking on condition of anonymity.
The violence came after a spate of bombings in and around Baghdad on Sunday killed at least 19 Iraqis and two American soldiers, according to security officials and the US army.
Violence is down dramatically in Iraq from its peak in 2006-7, but attacks remain common. A total of 211 Iraqis were killed in violence in April, according to official figures.