Cambodians voted in local polls on Sunday as a revived opposition party attempted to dent Prime Minister Hun Sen's decades-long grip on power ahead of national elections next year.

Hun Sen, one of the world's longest-serving leaders, has ruled Cambodia for more than 37 years and turned the country into a one-party state in 2018 when his party won every seat in a national election.

The prime minister was all smiles early in the day, voting in a polling station at a school on Phnom Penh's outskirts with his wife Bun Rany. He declined to speak to media.

Critics and rights groups have accused him of creating a climate of fear by locking up scores of political opponents and activists.

The opposition Cambodia National Rescue Party (CNRP) -- which won 44 percent of the popular vote in local elections in 2017 -- was forced to forfeit its positions after a court dissolved it later that year.

Scores of opposition figures have since fled the country, while others have been arrested.

Opposition leader Kem Sokha, who was arrested and jailed for more than a year, is facing a treason trial, while CNRP co-founder Sam Rainsy is living in France to escape convictions he says are politically motivated.

Sunday's vote in 1,652 communes, or village clusters, will take the country's political pulse ahead of the national elections in 2023.

At several polling stations in the capital Phnom Penh, an AFP journalist saw the ruling Cambodian People's Party (CPP) lead the main opposition party in large numbers, based on initial vote counts.

Voters cited peace and development in the country as they cast their ballot for Hun Sen's party inside schools or Buddhist temples.

"I picked the same old candidate, I did not change," said Srey Chan Samuth, 76. "We have been working together since the beginning, so we know who is good and who is bad."

A total of 17 parties are running in the local election, with more than 11,600 positions up for grabs -- the majority of which are presently controlled by the CPP.

But all eyes are on the performance of the Candlelight Party (CP) -- founded by Rainsy in 1995 -- which has registered candidates to contest in nearly all communes and has been gaining strong support.

All eyes are on whether the opposition can put a dent in Prime Minister Hun Sen's hold on power as Cambodians head to the polls
All eyes are on whether the opposition can put a dent in Prime Minister Hun Sen's hold on power as Cambodians head to the polls AFP / TANG CHHIN Sothy

"The Candlelight Party is the last hope for the people, although we are suffering from intimidation and threats, and political harassment," party secretary-general Lee Sothearayuth told AFP.

UN Human Rights Office spokeswoman Liz Throssell said she was disturbed by patterns of obstruction targeting opposition candidates ahead of the poll.

She warned that the CP "faces a paralysing political environment" after at least six candidates and activists were arrested in the run-up to the vote.

The CP is well-positioned to attract supporters and is the only party that "poses a realistic threat" to Hun Sen's CPP, said Sebastian Strangio, a journalist and author of a book on Hun Sen's rule.

"A strong opposition showing would demonstrate that the popular discontent with CPP rule continues to simmer beneath the surface of Cambodian politics," he told AFP.

CPP spokesman Sok Eysan, however, shrugged off the competition, telling AFP late Sunday his party had won the majority of positions.

"We did very well," he said, claiming his party would win around 90 percent of the votes.

But some voters said they wanted new faces to lead their communities.

"I voted for a change and social justice," one 35-year-old, who asked not to be named, told AFP.

The National Election Committee (NEC) said voter turnout was nearly 78 percent, with 7.1 million people casting a ballot.

Official results are not expected until June 26.