A court in Cambodia has sentenced a land rights campaigner and prominent journalist to 20 years in prison.

Mam Sonando, who owns Beehive, an independent radio station that often criticizes the government, was convicted on charges of inciting a rebellion by allegedly conspiring with the residents of Kratie province in the eastern part of Cambodia to form their own separate state.

Sonando, 71, was also fined 10 million riel ($2,500) by the Phnom Penh Municipal court.

"I am happy that I have helped the nation," Sonando told reporters as he departed the court following his conviction.

Sonando had been arrested in 2003 and 2005 on similar charges.

Human rights campaigners claimed the arrest and conviction of Sonando were fuelled by the government’s desire to stamp out any dissent in the country. The particular episode in Kratie, they assert, played amid a backdrop over a struggle for land, with local villagers outraged by the seizure of territory by rubber companies, on behalf of foreign investors.

Beehive Radio broadcast a report accusing the government of having committed crimes against humanity by forcibly evicting thousands of people in the Kratie region.

Clashes last May in the region between protesters and security forces led to the shooting death of a teenage girl.

"Our court has announced a verdict that is politically motivated," said Ou Virak, president of the Cambodian Centre for Human Rights (CCHR), according to Agence-France Presse. "There's no evidence that Mam Sonando has committed these offences."

Sonando, who is also the leader of the Association of Democrats (a pro-democracy movement), has long criticized Cambodian Prime Minister Hun Sen (who demanded Sonando's arrest earlier this summer).

Virak also declared: “Not only is this verdict a total violation of Mam Sonando’s human rights, it is also embarrassingly unsophisticated and brazen… 20 years is practically a life sentence in many countries, and a death sentence for a man of 70.”

Amnesty International also condemned Sonando's fate, calling it “shocking” and “baseless.”

“This verdict is inexplicable. No evidence was presented at the trial that proved that insurrection actually occurred or that Mam Sonando was involved,” said Rupert Abbott, Cambodia researcher at Amnesty International, who attended the trial, in a statement.

“Mam Sonando is a prisoner of conscience, convicted and imprisoned solely for the peaceful exercise of his right to freedom of expression through his radio broadcasts, and Amnesty International will be campaigning strongly for his release.”

Abbott added: “This unbelievable narrative of secession has been used to silence dissent. Today’s convictions mark a disturbing deterioration in the situation of freedom of expression in Cambodia.”

CCHR lamented a deteriorating climate in Cambodia for human rights this years, citing the murder of an environmental activist by the military in Koh Kong province in April, the shooting of women garment factory workers in Svay Rieng by the city governor’s forces and prison sentences handed out to Boeng Kak women who were protesting land seizures.

The U.N. Human Rights Council's Special Rapporteur for Cambodia said recently that the country's people are "increasingly desperate and unhappy" over land-rights abuses.

Hun Sen, who has ruled Cambodia since 1985, has vowed to stay in power for another three decades, when he reaches the age of 90, according to AFP.