Soaring nationalist sentiments have powered the campaigns, fuelled by a 10-day military standoff with neighbouring Thailand over a small patch of disputed land near the ruins of the 11th-century Preah Vihear temple.

The most frenetic campaigning took place in Kampong Cham province, home to one million of the eight million people registered to cast ballots Sunday.

Just after dawn Friday, thousands of opposition supporters waved flags and rode through the town of Kampong Cham on the backs of trucks and motorcycles, blaring party policies from speakers.

The day wound down with a candlelight vigil in Phnom Penh, with Sam Rainsy supporters wearing white shirts and caps bearing the party's candle logo.

But few expect voters to oust the Cambodian People's Party (CPP), which has ruled since the fall of the genocidal Khmer Rouge nearly three decades ago.

Hun Sen has held the top job for 23 years, and voters are widely expected to hand him another five-year term.

His party loudly touts recent economic growth in Cambodia, one of the world's poorest countries, which has averaged 11 percent over the last three years.

Tensions over Preah Vihear only enhanced Hun Sen's standing, helping the CPP portray itself as the defender of the nation.

"The voters realise we did a lot -- building roads, schools, health care, and especially the economy. Preah Vihear is the latest thing," Phnom Penh mayor Kep Chuktema told an early CPP rally in the capital.

"We saved the lives of Cambodian people from the genocide. We gave people lives. From zero in 1979, Phnom Penh now has everything. From ghost city, now Phnom is a very good city," he said, with music blaring as 10,000 CPP supporters filled a riverside boulevard with a carnival atmosphere.

Although the CPP is tipped to win a large majority, the party mounted a massive campaign, parading in shiny new vehicles while covering the country with posters and the airwaves with promises of further development.

"The CPP campaigns are much fancier than those of other parties... The CPP outsmarts other political parties because those parties haven't achieved much at all," said Neang Sovath of the election monitoring group Comfrel.

More than 13,000 domestic and international observers are set to monitor the 15,000 polling stations.

The campaign has seen fewer irregularities and less violence than in the past, monitors say, partly because the nation is more stable, with garment exports and tourism helping pull Cambodia from the ashes of civil war.

Hun Sen's CPP expects to expand its control over the 123-seat parliament, hoping to add eight seats to the 73 it already holds, which would cement his ruthless drive to secure his grip on power.

He lost Cambodia's first elections, backed by the United Nations in 1993, but bargained his way into a power-sharing deal and then reasserted total control in a 1997 coup.

Hundreds of people were killed in the run-up to elections the following year. Protests against the CPP victory were put down violently.

The last national election in 2003 was less violent but plunged the kingdom into a year of political stalemate that resulted in a coalition with the royalist Funcinpec.

The royalists have since imploded over internal scandals, while Sam Rainsy is expected to win few votes outside the capital.