BAGHDAD - A brazen robbery attempt in Baghdad and a series of attacks on security forces in the north killed six people and wounded dozens more Wednesday, raising tensions in the run-up to parliamentary elections.

The attacks come as Iraq awaits a final decision on whether hundreds of candidates -- most believed to be members of the once-dominant Sunni Arab minority -- will be barred from contesting next month's parliamentary election. U.S and Iraqi officials say barring Sunni candidates from the March 7 vote could cause political instability.

A gang targeted a jewelry store in eastern Baghdad, with one attacker tossing a grenade inside while the others waited outside in a car, police said.

Police nearby heard the commotion, however, and opened fire on the men before they could rob the store. The gun battle that followed killed a policeman, the storeowner and his assistant, and wounded six others.

The grenade thrower was shot and is being questioned at the hospital, but his accomplices escaped, said police.

Despite an overall decline in Iraq's violence since 2008, insurgents have routinely targeted security forces while heavily armed criminals, often former rebels, occasionally carry out bold daylight robberies. Some insurgents have turned into armed criminal gangs, preying in particular on jewelry stores in heavily armed assaults.

The afternoon heist was a dramatic snapshot in a day of attacks around Iraq.

Earlier in the day, a roadside bomb struck a patrol in the disputed northern city of Kirkuk, killing a police lieutenant, a police official said. Two police also were wounded in the attack 290 kilometres northwest of Baghdad, he added.

Meanwhile, authorities said at least 25 people were wounded when a suicide bomber detonated a vehicle near an Iraqi army and police post in Mosul, about 360 kilometres northwest of Baghdad. Ten civilians were among the wounded, a police official said. A second bomb was discovered in downtown Mosul, a second official said, but it was dismantled by security forces.

Hours later, in Mosul's Wadi Hajar neighborhood, a sticky bomb blew up the private car of an off-duty policeman, killing him, authorities said. Another off-duty policeman was shot and killed by gunmen in the center of Mosul.

All security officials spoke on condition of anonymity because they were not authorized to release the information.