PHNOM PENH (Reuters) - Cambodia’s highest court dissolved the main opposition party on Thursday, leaving authoritarian Prime Minister Hun Sen clear to extend more than three decades of power in next year’s election as rights groups decried the death of democracy.

The government had asked the Supreme Court to dissolve the Cambodia National Rescue Party (CNRP), which was accused of plotting to take power with the help of the United States after the arrest of party leader Kem Sokha on Sept. 3.

The court ruling also ordered a five-year political ban for 118 members of the opposition party, which had posed a major election threat for Hun Sen, a former Khmer Rouge commander who is the world’s longest-serving prime minister.

In a televised address, Hun Sen told Cambodians the election would go ahead “as normal.”

The CNRP rejected the accusations against it as politically motivated. It did not send lawyers for the court ruling.

“Democracy was brought to trial and it lost,” said Mu Sochua, a deputy to Kem Sokha who fled Cambodia fearing arrest.

“The international community must fulfill its commitments to democracy, human rights and freedoms. Sanctions are the best leverage for negotiation for free, fair and inclusive elections.”

Western donors, who sponsored elections overseen by the United Nations in 1993 in the hope of founding an enduring democracy, had called for Kem Sokha’s release.

But they have shown no appetite for sanctions against Cambodia’s government, which is now closely allied to China.

The United States and European Union missions in Cambodia declined immediate comment on the court ruling.

Senator John McCain, a leading U.S. Republican, said the dissolution of the CNRP meant there was “no way the elections scheduled for 2018 can proceed in a manner that is free or fair,” and the Trump administration should impose sanctions.

“The Trump administration should move quickly to sanction all senior Cambodian government officials responsible for violating human rights and subverting freedom in Cambodia,” he said in a statement.

U.N. spokesman Farhan Haq said it was up to the government to provide a free environment without fear for fair elections.

Despite ramping up anti-U.S. rhetoric and linking the United States to the alleged plot against him, Hun Sen lauded U.S. President Donald Trump at a regional summit at the weekend and said he welcomed his policy of non-interference.

Dozens of police manned barriers outside the gold ornamented court in the center of Phnom Penh on Thursday. There was no sign of protests.

‘PEOPLE ARE SCARED’

Few people on the streets wanted to talk about the ruling, the latest chapter in decades of maneuvering that have kept Hun Sen and his Cambodian People’s Party (CPP) in power across all levels in the country of 16 million.

Police officers stand guard at the Supreme Court during a hearing to decide whether to dissolve the main opposition Cambodia National Rescue Party (CNRP), in Phnom Penh, Cambodia, November 16, 2017. REUTERS/Samrang Pring

“People are scared to talk amongst themselves,” said Seang Menly, 39, a driver of one of the rickety tuk-tuks that ply the streets of Phnom Penh. “In my neighborhood, people who used to give money and food to the CNRP no longer dare to.”

Hun Sen and his defenders say only he can ensure peace.

During his rule since 1985, Cambodia has been transformed from a failed state in the wake of Khmer Rouge purges and genocide to a lower middle-income country with growth of about 7 percent a year. Life expectancy has risen from 50 to 70.

“The Supreme Court’s decision today is not to end democracy but to deter extremists in order to protect the people and the nation from destruction,” said Huy Vannak, undersecretary of state at the interior ministry.

Rights groups condemned the decision by the court, which is headed by a judge who is a member of the ruling party’s permanent committee. They said it left Cambodia as a de facto one-party state and rendered next year’s election meaningless.

“This is the death of democracy in Cambodia,” said Phil Robertson of Human Rights Watch.

More than half the CNRP’s members of parliament had already fled Cambodia, fearing detention in a crackdown on Hun Sen’s critics, civil rights groups and independent media that began last year.

“We don’t know who is next,” an editor at the Voice of Democracy radio station in Phnom Penh said. It was taken off the air in August, but has continued broadcasting through Facebook.

The CNRP’s parliamentary seats will be redistributed to other government-aligned parties after its dissolution.

The party will also lose control of the councils that it won in local elections in June, when its strong showing in winning more than 40 percent of them made clear the threat it posed to the ruling party next year.

Hun Sen appealed to CNRP members to join the CPP, saying: “You cannot even save your party. How will you save yourself?”

Evidence presented against the party included a video from 2013 in which Kem Sokha said he had help from unidentified Americans to win power. He said he was talking about a democratic election strategy, not a coup.