Voters in the Democratic Republic of Congo have begun casting ballots in presidential and legislative elections, after violence and accusations of fraud marred the run-up to Monday's vote.

The head of the country's electoral commission said Sunday there was no evidence of fraud, after at least one opposition candidate said vote tampering was under way favoring incumbent President Joseph Kabila.

At least three people were reported killed leading up to the election.

Police in the southeastern city of Lubumbashi said gunmen attacked two election vehicles early Monday and set them on fire.

This is only the second multi-party poll since the large central African nation was torn apart by two wars following independence. The last war ended in 2003.

Mr. Kabila, who is running against 10 opposition candidates, is widely expected to win re-election. Results are expected by December 5, the day before Mr. Kabila's current term ends.

President Kabila has been in power since 2001, when he assumed the presidency after the assassination of his father, Laurent Kabila. He won a presidential vote in 2006.

His strongest challenger, long-time opposition leader Etienne Tshisekedi, backed down from plans to hold a rally Sunday in the capital, Kinshasa, in defiance of a ban on campaigning the day before the election. His advisers say they feared for his safety. On Saturday, Congolese police blocked Mr. Tshisekedi and his supporters from leaving the airport for several hours. They fired bullets and tear gas, killing three and wounding several more.

The capital was reported calm on Sunday, described as a “Day of Reflection” in Congo, with no gatherings of large crowds.

Mr. Tshisekedi has accused the head of the United Nation's large peacekeeping force in Congo of a bias against him. He has called for removal of mission chief Roger Meece, who once served as the U.S. ambassador in the county.

More than 18,000 candidates are vying for 500 seats in the general assembly.