Scores of ethnic minority Montagnard people have been hiding in the jungle in Cambodia after fleeing repression in Vietnam, according to UN officials.
Many have been living in the jungle since April, when the Hanoi government cracked down on protests against land confiscation and religious persecution.
According to the UN, 123 Montagnards have now been lured from hiding.
But human rights groups claim there could be many more still living secretly in the province.
Last week, the Cambodian government gave UN officials permission to visit the remote province of Ratanakiri, in north-east Cambodia, where the refugees are thought to be living.
The government initially labelled the Montagnards - a Christian minority group - as illegal migrants, and refused requests from aid workers and journalists to visit the region and assess the situation.
But after continued pressure from King Norodom Sihanouk, diplomats and human rights groups, the UN refugee agency, the UNHCR, was allowed to reopen its office in the provincial capital Banlung last week.
The UN team quickly found more than 40 Montagnards hiding in the trees - and have continued to find many more since.
Cathy Shin, UNHCR officer, said: "Everyone is quite exhausted. They've been hiding in the forest for a month to two months, and there are some very sick people in the group."
The Montagnards complain of repression from Hanoi
According to local media reports, the refugees have survived by eating leaves, wild mushrooms or food secretly brought to them by Cambodian hill tribes.
"They looked ill and starving, after hiding with a shortage of food and eating tree leaves," said Pen Bunna, an official with the Cambodian human rights group Adhoc.
UN workers and government officials will now interview the Montagnards to decide whether they should be treated as asylum seekers and sent to the Cambodian capital Phnom Penh.
The Montagnards say they have been persecuted by the Vietnamese government ever since they supported the American forces during the Vietnam War nearly 30 years ago.
But the situation has got worse since April this year, when a group of Montagnards held peaceful demonstrations over the Easter weekend, demanding land and religious rights.
According to the campaign group Human Rights Watch, dozens of Montagnards were killed in an ensuing crackdown - although the Vietnamese government insists only two people died.
"I fled because I'm Christian and I had problems with my land," said 30-year-old Ralanpee, one of the refugees in Cambodia. "If I get sent back, I think they will kill me."
"I would be happy to die right here, rather than go back to Vietnam and die there," he told Reuters news agency.
The exodus to Cambodia mirrors the situation in February 2001, when more than 1,000 Montagnards fled Vietnam following a government crackdown.