PHNOM PENH, April 29 -- A Cambodian court rejected an appeal on Thursday by detained opposition leader Kem Sokha against his nearly three-decade sentence for treason, his lawyer said, a conviction rights groups say is politically motivated.

The 72-year-old politician was convicted for trying to topple the government of long-ruling former prime minister Hun Sen, who is the father of the current leader and remains an influential figure in national politics.

He was sentenced in 2023 to 27 years in prison for treason but was ordered to serve the time under house arrest in the capital Phnom Penh.

The co-founder of the dissolved opposition Cambodia National Rescue Party (CNRP), Kem Sokha has repeatedly denied the charge since his 2017 arrest...