At least three mortar rounds were fired at voting centres in Salahuddin province, a Sunni stronghold that was home to toppled dictator Saddam Hussein, as Iraq began a parliamentary election on Sunday, police said.
Three people were wounded by the explosions in the town of Baiji, 180 km north of Baghdad, they said.
Voting across the ethnically and religiously divided country began at 7 a.m. (0400 GMT).
The election, Iraq's second for a full-term parliament since the 2003 U.S.-led invasion, is viewed as pivotal as the country tries to end sectarian violence and set the stage for stability and economic growth ahead of a U.S. withdrawal by end-2011.