Hun Sen, who has been in power for nearly three decades, was among the early voters, casting his ballot just after the polls opened near his home in Takhmau, just south of the capital, Phnom Penh.
Opposition leader Sam Rainsy, who returned from self-exile this month, began his day with a visit to a polling station near his party's office in Phnom Penh. Hundreds of voters, particularly younger ones, greeted him enthusiastically, with some of the bolder ones hugging him.
Counting of the paper ballots at polling stations began shortly after the polls closed at 3 p.m., with representatives of political parties witnessing the process. The first unofficial results were not expected until Sunday evening.