A shoot-out between a group of opposition and government supporters in the island's south early Thursday damaged a vehicle, but caused no injuries, CMEV spokesman D.M. Dissanayake said.
Most complaints were against the ruling United People's Freedom Alliance led by President Mahinda Rajapakse.
"Pro-government supporters are reported to have intimidated voters," Dissanayake said, adding that in some places unidentified men had grabbed polling cards from those trying to cast their ballots.
He said dozens of war-displaced people in state-run makeshift shelters were without transport to get to polling booths.
The private People's Action for Free and Fair Elections reported cases of pro-government supporters chasing away polling agents belonging to opposition parties.
More than 14 million people are eligible to vote, with 7,620 candidates from 36 political parties and 310 independent groups running for parliament. First results are expected by midday Friday.
Police had deployed 60,000 constables and kept another 20,000 military personnel on alert to deal with any major outbreak of violence during the nine-hour voting period.