Malaysia on Tuesday started returning about 1,500 Myanmar nationals, a scheme that rights groups warn could endanger migrants sent back to a country at war.
The first group forms part of a plan to repatriate 5,000 Myanmar citizens who, Kuala Lumpur says, agreed to "voluntary" returns from detention centers as anti-migrant sentiment surges in Malaysia.
Advocacy groups argue that harsh conditions in detention centers may have forced their decisions, and they could face dangerous homecomings in Myanmar, where war has continued since 2021.
Neither government has confirmed how many Rohingya are in the first group. Rights groups fear those returned could face persecution that they describe as genocide.
Dozens of buses arrived under police escort on Tuesday at the Majlis Perbandaran Manjung stadium close to the Lumut naval base in northwestern Malaysia, Agence France-Presse (AFP) correspondents saw.
Officials will process the migrants at the site before moving them to a nearby facility for the sea voyage to Myanmar.
Boats should reach Thanlyin Navy Base just south of Yangon around the end of this week, a security source in Myanmar said on condition of anonymity because the person lacked authorization to speak to the media.
Marine traffic websites showed the country's hospital and auxiliary support vessel Than Lwin anchored just off the naval base.
Rohingya, a persecuted Muslim minority, make up two-thirds of the 190,000 Myanmar refugees and asylum seekers in Malaysia, according to the United Nations.
Prime Minister Anwar Ibrahim announced in July that Myanmar consented to receive 5,000 Rohingya. The plan emerged after authorities detained more than 100 Rohingya who had gathered outside the UN refugee agency's office in Kuala Lumpur.
Myanmar earlier this month pledged "safe and dignified" returns for its citizens displaced abroad after criticism from the UN and rights groups.
Last week, more than 160 civil society groups urged Malaysia in a joint statement to "immediately halt the deportations," pending talks with civil organisations about the situation on the ground in Myanmar. Malaysian immigration detention depots held 10,388 Myanmar nationals by mid-August, the ministry said, with not all considered refugees.
Although it shelters one of Southeast Asia's biggest refugee populations, Malaysia never signed the 1951 Refugee Convention and does not formally recognise refugee status.
AFP fact-checkers found that Rohingya refugees in Malaysia have been targeted by online disinformation campaigns that rights advocates say are fuelling xenophobia and intimidation. Hundreds of thousands of Rohingya, a mostly Muslim group, fled Myanmar in 2017 after a brutal military crackdown that now underpins a genocide case at the International Court of Justice.
Bangladesh hosts more than 1.2 million Rohingya in the world's largest refugee settlement, but talk of repatriations from there has yielded little progress.