The easing of restrictions comes a day after Sam Rainsy, a co-founder of their now-banned opposition party, flew into the region from self-imposed exile saying he aimed to return home to rally opponents of authoritarian ruler Hun Sen.

Cambodia has also been under pressure to soften a political crackdown as the European Union considers whether to go ahead with potentially damaging cuts to trade preferences.

The Phnom Penh Municipal Court said in a statement that Kem Sokha could leave his house, but that he could not engage in political activity or leave the country.

"He can travel anywhere but can't leave Cambodia," Justice Ministry spokesman Chin Malin told Reuters. "This is because he has been cooperative with the authorities."

Kem Sokha, 66, was arrested in 2017 and the Cambodia National Rescue Party (CNRP) was banned in the run-up to a general election last year that Hun Sen's ruling party then swept but which was condemned as a farce by Western countries.

Hun Sen, 67, a former Khmer Rouge commander, has ruled the country of 16 million for more than 34 years with an iron hand and a wily ability to play off his opponents against each other and sow division among them.

Sam Rainsy, 70, flew into Malaysia on Saturday and told supporters to "keep up the hope" after promising to return home with other exiled opposition leaders to challenge Hun Sen.

In Malaysia, Sam Rainsy was meeting officials to discuss strategy on Sunday. CNRP officials there said they had no immediate comment on the easing of restrictions on Kem Sokha.

Australian Associated Press