The Phnom Penh Post reported the Cambodian People's Party led by Hun Sen, 60, had its hold on the National Assembly weakened considerably, winning only 68 of the 123 seats in Sunday's fiercely contested elections, 22 fewer seats than it won in 2008. The newspaper said the CPP's royalist coalition partners did not win any seats.
Preliminary results showed while the ruling CPP won 68 seats the opposition Cambodia National Rescue Party (CNRP) got the remaining 55 seats, Cambodian government spokesman Khieu Kanharith said.
CNRP leader Sam Rainsy, 64, urged his people to remain calm and wait for the official results and not resort to violence. The French-educated leader who had been in exile returned to Cambodia recently after being granted a royal pardon on various charges.
During the campaign, Sam Rainsy's party had promised to end corruption and promote jobs for young people.
Hun Sen's CPP has taken credit for the economic progress and stability that have made the country one of the fastest-growing economies in the region, but the party has been hurt by land conflicts and allegations of corruption.
Elections have been held in Cambodia since the 1990s. Prior to that the country was ravaged by wars followed by four years genocide from 1975 to 1979 under the brutal Khmer Rouge rule, which was overthrown with the backing of Vietnam. The genocide is estimated to have claimed nearly 2 million lives, dramatically portrayed in the movie "Killing Fields."
The Post said Sunday's election figures posted on websites showed the opposition won in four provinces of the capital Phnom Penh, Kampong Cham, Prey Veng and Kandal, and also had made inroads into CPP strongholds.
Sam Rainsy's wife, Tioulong Saumura, a CNRP lawmaker, told the Post the elections were "a big victory, even if we were to accept those figures that have come in violation of the law."
There were not many instances of violence, but the Post said the alleged irregularities were reported by some election monitors. The newspaper said observers recorded voter list problems, unusual numbers of police personnel at polling stations and at least two stations that were moved without prior notice.
Representatives from the International Conference of Asian Political Parties lauded the election, the Post said.
Eight political parties contested in the elections, with an electorate of more than 9 million.
The New York Times said the elections may have ended the country's years of splintered opposition and helped bring a two-party system.
Cambodia historian David Chandler told the Times for the past 28 years, Hun Sen has used a combination of political threats and intimidation, while delivering tangible improvements in people's lives.
"There are more roads, more factories, more motorcycles -- the patronage flows down and the loyalty flows up," Chandler said.
Karona Pok, a 32-year-old receptionist at a charity, told the Times she had voted for the governing party because "we wouldn't be here today." She credited Hun Sen and Vietnam for ousting the Khmer Rouge.