Updated

Cambodian Prime Minister Hun Sen on Friday wrapped up campaigning for re-election by attacking an opposition call to boycott the polls and calling those who heed it "destroyers of democracy."

Some 8.3 million people are registered to vote in Sunday's general election to fill 125 seats in the National Assembly.

Hun Sen's Cambodian People's Party is expected to win easily after a court last year dissolved its only credible opponent, the Cambodia National Rescue Party, on charges that it conspired with the U.S. to overthrow the government.

Critics say the move was part of a long-planned strategy to remove all obstacles to Hun Sen continuing to rule the country he's dominated politically since first becoming prime minister in 1985.

In the last general election in 2013, the opposition CNRP came close to pulling off a surprise victory, winning 44 percent of the popular vote.

The poll is widely seen outside Cambodia as a sham. The United States and the European Union have declined to help fund it, though Japan has contributed.

The CNRP has advised Cambodians not to vote, a boycott the ruling party's leaders fear of heeded, would deeply embarrass them and badly undermine their victory.

Speaking in front of a large crowd — 150,000 strong, according to its organizers — Hun Sen said, "People who listen to the words of the country's betrayers, and don't vote, are the ones who destroy democracy in Cambodia.

"You will regret it. So I suggest all Khmer citizens think about that, because the majority of people will vote but the ones who don't vote, how will they live with those who do?"

He said peace and development were the priorities for his party.

Twenty parties in all are on Sunday's ballot, but apart from Hun Sen's CPP, most are small, under-resourced or almost completely unknown. Some are said to be proxies, set up by the ruling party to give the semblance of a contest.

Preliminary results are expected on Sunday night.

Hun Sen's party has been dominating Cambodia's political scene, but its election maneuvering has brought some sharp rejoinders from abroad.

The U.S. Congress this past week passed the Cambodia Democracy Act "to promote free and fair elections, political freedoms and human rights in Cambodia and impose sanctions on Hun Sen's inner circle."

The measure, which strongly condemns Hun Sen's regime, would bar individuals designated by President Donald Trump from entering the U.S. and blocks any assets or property they may possess. Its suggested list of those who should be sanctioned includes Hun Sen, several of his close family members, and about a dozen other top officials and military officers.

Cambodian officials and ruling party members rejected the measure as counterproductive interference into Cambodia's internal affairs.

Japan, traditionally more reluctant than Western nations to criticize Cambodia's government, announced this past week it would not be sending election monitors for Sunday's polls.Although there was no clear explanation for the decision, it is seen as a low-key but unexpected criticism of the election process.

Hun Sen became prime minister in 1985 and has led Cambodia ever since with a combination of skill, guile and ruthlessness.

He is a former Khmer Rouge field commander. He defected to Vietnam during the disastrous rule of Pol Pot, later returning to help overthrow the regime.