Cambodia's ruling party was poised to win yesterday's election with 82.17 per cent of voters having cast their ballots, in spite of a sustained campaign by political exiles for a boycott of the election.

While preliminary results of the election are not expected until next month, the ruling Cambodian People's Party (CPP) is widely expected to retain its grip on power given the vast advantage it has over the 19 other small political parties in the race.

CPP spokesman Sok Eysan told Reuters the party won an estimated 100 out of 125 parliamentary seats. "The CPP won 80 per cent of all the votes and we estimate we will win no less than 100 seats," he said.

The CPP's strongest challenger in recent years, the Cambodia National Rescue Party (CNRP), was dissolved by a court ruling in November last year and its former president Kem Sokha remains in pre-trial detention after being arrested last September for alleged treason.

Human rights groups and many CNRP leaders who fled overseas after the crackdown labelled it a "sham election" and urged voters to stay away, casting voter participation as a barometer of the government's legitimacy.

Caretaker Prime Minister Hun Sen has been in power since 1985.

At 5pm yesterday, the National Election Committee (NEC) revealed that 6.89 million out of 8.38 million registered voters had cast their ballot.

The 82.17 per cent voter turnout yesterday was higher than the 69.6 per cent achieved in the 2013 general election, but short of the 90 per cent recorded in last year's commune election.

In a message posted on Facebook yesterday afternoon, France-based former CNRP president Sam Rainsy wrote that the voter turnout "does not reflect reality" because voters were intimidated and threatened, and "the manipulation of voting in the polling stations… caused serious distortion".

"The result of this false election conducted in a climate of fear is a betrayal of the popular will," he wrote.

NEC chairman Sik Bun Hok denied voters were intimidated.

"All of you can see (Cambodians') expressions and hear their words, about how they feel towards voting, in the news broadcasts," he told reporters at a press conference. "You shouldn't think that everything the opposition says is right… See the election result."

According to the election agency, polling went on "without disturbance" nationwide and some polling centres even closed before the designated time of 3pm because all their designated voters had turned up early.

In Phnom Penh's Stung Meanchey commune yesterday, voters massed at polling booths even before voting began at 7am. One voter, Mr Sem San, a 21-year-old baker, told The Straits Times: "Those smaller parties have fewer supporters, but it doesn't mean they have no supporters."

By the wind-swept riverside in Phnom Penh, where Mr Chay Dara cast his vote, the 32-year-old hotel general manager told The Straits Times he thought little of allegations that this was a sham election.

"I have my own parliamentarians to vote for," he said. "I vote for the development of this country."

The CNRP won 55 out of the 123 Parliament seats in the 2013 election, with rest going to the CPP.

In this election, 125 seats are up for grabs.

Since 2013, Mr Hun Sen has raised the wages of public servants, commune councillors and workers in the crucial garment and footwear industry.

But critics say this has been matched by a crackdown on political opposition and independent media. Over the past year, several independent outlets, citing pressure from the government, have ceased operations. On Saturday, officials confirmed to Voice of America journalists that they had ordered Internet service providers to block access to at least 15 websites, including the Voice of America's Khmer service, the Radio Free Asia's Khmer service, and the Voice of Democracy.

ISEAS - Yusof Ishak Institute visiting fellow Chheang Vannarith, who was in Phnom Penh to observe the elections, said the turnout rate was "very surprising".

He said: "Cambodians have expressed their view of democracy, peace and development, because they believe that multi-party democracy system is still alive."

Mr Bun Hok, meanwhile, challenged overseas critics: "The international community was waiting to see what were Cambodians' real wishes. And Cambodians have made their wishes clear (with this voter turnout).

"Will the international community still persist in activities against the wishes of Cambodians?"