PHNOM PENH, Cambodia -- Cambodian Prime Minister Hun Sen's ruling party has claimed victory in Sunday's election after soundly defeating opposition efforts to unseat him. Meanwhile, high-level diplomatic talks with Thailand regarding a flaring border dispute got under way.

As final vote counting continued, the Cambodian People's Party (CPP) seemed assured of winning 90 seats in the 123-seat parliament, easily surpassing the minimum 50-percent-plus-one-seat required to govern outright, while the Sam Rainsy Party (SRP) was expecting to win at least 30 seats.

The balance would be split between the Human Rights Party (HRP) and the Norodom Ranariddh Party (NRP), while the royalist Funcinpec party performed abysmally and returns to the National Election Committee (NEC) show it may not even win a single seat.

However, those four opposition parties -- The SRP, NRP, HRP and Funcinpec -- also said they would reject the results amid claims that thousands of names were missing from voter registration papers.

They said in a statement the polls "were manipulated and rigged by the CPP" and that the NEC is a CPP tool to present "a façade of democracy."

"We call on the public opinion to condemn the tricks and maneuvers."

Despite the killing of one journalist during the campaigning, most election observers say this election campaign had seen much less violence than polls in 2003, 1998 and the U.N.-sponsored vote in 1993.

They noted some irregularities, but most had not announced their final assessment on whether the poll was free and fair.

In claiming victory, CPP spokesman Khieu Kanharith said it was beyond doubt his party would win, ushering in another term for Hun Sen, who is already Southeast Asia's longest-serving leader, with 23 years to his credit.

Hun Sen took a vow of silence throughout campaigning but made one exception while casting his vote at a local school in Takhmao, 10 kilometers south of here.

"So far the atmosphere is good," he told reporters. "And I hope that today until the end of the voting and the counting of ballots the election will go smoothly across the country."

Official counting can last a month.

The win was widely seen as a vote of confidence in Hun Sen's handling of Cambodia's burgeoning economy -- seen as a legacy of 10 years of peace and relative stability -- and in particular the armed standoff with Thailand over the disputed temple at Preah Vihear in the country's remote far north.

Ruins from the 11th century temple sit 700 meters inside Cambodia under a border agreement struck between Bangkok and French-controlled Phnom Penh in 1908. But Thailand was never completely happy with the deal.

In 1962, an international court ruled the ruins belonged to Cambodia. The dispute flared again earlier this month when UNESCO responded to lobbying from Phnom Penh and against Thai wishes and listed Preah Vihear as a World Heritage site.

That decision could not have come at a better time for 57-year-old Hun Sen, whose bureaucrats were negotiating late Monday with emissaries from Thailand in the northwest town of Siem Reap.

All Cambodian political parties campaigned on Preah Vihear, but as Cambodians from all walks of life protested what was perceived as Thai belligerence, it was Hun Sen who countered Bangkok and reinforced the site with local militias formed out of battle-hardened former Khmer Rouge.

Chea Vanath, an independent analyst and former president of the Phnom Penh-based Center of Social Development, said the prime minister had handled the crisis well.

"It made him and the ruling CPP look good," she added.

Diplomatic sources said a bilateral resolution was preferred despite Cambodian efforts to have the U.N. Security Council rule on the dispute.

"I also think some pressure could be applied on the parties involved to find a settlement, this might help. It should be stressed that most countries do not want to be seen as supporting one over another," one source told World Politics Review.

However, both sides are playing it tough in Siem Reap -- which is also home to Cambodia's famed Angkor Wat -- and few observers are forecasting a breakthrough in the talks.

"Regardless of modern-day legal agreements, the Thais and Khmers have actually been fighting over this temple for 900 years and its not something that will be resolved overnight in Siem Reap. But if they stop pointing guns at each other then that would be a help," the source added.