PHNOM PENH (AFP) - Cambodian Prime Minister Hun Sen admitted on Monday that he will not make good on a US$5,000 (S$6,672) debt he lost on the recent bout between Floyd Mayweather and regional hero Manny Pacquiao because he was so incensed by the match outcome.

The 62-year-old strongman delivered a nine-minute rebuke of judges who ruled Mayweather had squarely beaten Pacquiao in Las Vegas on Saturday.

Echoing many of Pacquiao's Filipino compatriots who have also cried foul, Hun Sen accused the American officials of being biased towards Mayweather in the US$400 million fight.

"Yesterday, us viewers could barely give a point for Floyd, but the three judges unanimously decided Floyd was the winner," he said.

Hun Sen said he had made a US$5,000 bet with an official on the match outcome, a bet he would no longer honour.

"I would not settle this, I will not give you the money," he said without giving further details.

The admission is somewhat surprising given gambling is technically illegal in Cambodia outside of licensed casinos - although there is a thriving black market for betting on everything from the English Premier League to local cock fights.

The strongman's betting habits were not lost on many Cambodian social media users.

"Hun Sen violated the betting rules by gambling on boxing," wrote one Facebook user So Naro.

Hun Sen has ruled Cambodia with an iron fist for the last 30 years, tolerating little opposition. He is a known for his love of sports, particularly football, and has previously broken off from speeches to give his thoughts on a recent match or surprise score.