Cambodia's Prime Minister Hun Sen gestures during his visit to Phnom Penh Special Economic Zone on the outskirts of Phnom Penh, Cambodia. Picture: AP Photo/Heng Sinith, File

Phnom Penh - Cambodia's Supreme Court dissolved the main opposition Cambodia National Rescue Party on Thursday, dealing a devastating blow to a party that had been poised to challenge the long-term rule of Prime Minister Hun Sen in an election next year.

"The Supreme Court has decided to dissolve the Cambodia National Rescue Party and ban 118 individuals ... from doing political activities for five years starting from the day of this verdict announcement," a judge said.

The CNRP was accused of plotting to topple the government - which it denied.

The opposition party did not send lawyers to Thursday's court session.

Critics see the verdict as the culmination of months of pressure on the opposition, civil society and independent media by the ruling Cambodian People's Party (CPP) in an attempt to quell the opposition ahead of the 2018 general election, which was expected to be Hun Sen's biggest challenge to his more than 30-year rule.

There were no signs of protest outside the court following the verdict.