Iraq's interim president Ghazi Yawer was one of the first people to vote in the country's first multi-party elections for half a century.
Mr Yawer said he hoped all Iraqis would follow his lead and go to the polls.
Over 100 parties and coalitions are competing for 275 seats in a transitional national assembly which will draw up a new constitution.
But militants seem to have already begun a promised bombing campaign, with blasts in Baghdad and other cities.
Iraqi police reported a suicide car bomb attack on a polling station in western Baghdad soon after the polls opened. One police officer was killed along with the bomber.
Mortar fire has also been heard in Mosul, Basra and Baquba.
They came after militant leader Abu Musab al-Zarqawi issued a warning to Iraqis not to vote, and declared "all-out war" on the election.
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