Fresh attacks were launched soon after polls opened on Wednesday morning, killing seven people and wounding 24.
Security officials reported more than 40 attacks in total, including mortar fire, roadside bombs and a suicide blast, all targeting polling stations or voters on their way to them in northern and western Iraq, Al-Akhbar reported.
North of Baghdad, militants seized a polling station and blew it up, after expelling election staff and those waiting to vote.
Long queues formed from early morning at tightly-guarded election centers despite a spate of attacks in recent days on polling booths and campaign gatherings.
The run-up to the election, the first since US forces departed in December 2011, has seen Baghdad and other major cities swamped in posters and bunting.
A surge of violence in the run-up to the polls, including militant attacks in the past two days which killed 90 people, had spurred fears that much of the electorate could stay home rather than risk being targeted.
More than 750 people have been killed this month, with unrest at its worst since Iraq emerged from a brutal internal conflict that left tens of thousands dead in 2006 and 2007.
Voting, which began at 7:00 am, is to be continued to 6:00 pm, as upwards of 9,000 candidates compete for 328 parliamentary seats.