Cambodian Prime Minister Hun Sen will start a visit to Myanmar on Friday for talks with its military rulers, triggering protests across the conflict-torn nation by coup opponents who fear his trip will provide more legitimacy to the junta.
His visit will be the first by a head of government to Myanmar since the army overthrew the elected administration of Aung San Suu Kyi on 1 February last year, sparking months of protests and a bloody crackdown.
Cambodia is current chair of the Association of Southeast Asian Nations, which has been leading diplomatic efforts to resolve the crisis in Myanmar and which adopted a five-point "consensus" peace plan in April.
Some other ASEAN countries including Indonesia have expressed frustration at the junta's failure to implement the peace deal, which has fanned divisions in the 10-member bloc.
In Myanmar, opponents of military rule have said Hun Sen is backing the junta by making the trip.
In Depayin, about 300 km (186 miles) north of the capital Naypyidaw, protesters burned a poster of the Cambodian prime minister and chanted "Hun Sen don't come to Myanmar. We don't want dictator Hun Sen", photographs on social media showed.
There were also reports of protests in Mandalay and the Tanintharyi and Monywa regions.
In a speech on Wednesday, Hun Sen called for restraint from all sides in Myanmar and for the peace plan to be followed through.
"Brothers in Myanmar, do you want your country to fall into a real civil war or want it solved?" he said. "The first point of the consensus is the patience, the cessation of violence. This is the goal that we want."
After a phone call this week with Hun Sen, Indonesian President Joko Widodo said in messages on Twitter if there was no significant progress in the peace plan only non-political representatives from Myanmar should be allowed at ASEAN meetings
Min Ko Naing, a leading activist in Myanmar, said in a social media post that Hun Sen would face massive protests over his visit, which would hurt ASEAN.
The General Strike Coordination Body, which pools more than 260 organisations opposed to the coup in Myanmar, also denounced Hun Sen's visit, accusing him of backing Myanmar's military rulers.
Hun Sen is one of the world's longest serving leaders and Western countries and human rights groups have long condemned him for crackdowns on opponents, civil rights groups and the media in Cambodia.
Amnesty International's Deputy Regional Director for Research Emerlynne Gil said Hun Sen should cancel his trip and "lead ASEAN to strong action to address the country's dire human rights situation".
The Cambodian foreign ministry said Hun Sen will meet military leader Min Aung Hlaing, but the US-funded RFA (Radio Free Asia) cited a junta spokesman as saying he would not meet Suu Kyi, who is on trial and faces nearly a dozen cases that carry a combined maximum sentences of more than 100 years in prison.