"I am extremely concerned about the fate of people who attempt to come into this country with the illusion that they will reach safety," Jean-Marie Fakhouri, head of the U.N. High Commissioner for Refugees (UNHCR) Asia-Pacific region, told a news conference.

"At this point in time, the asylum space in Cambodia for a seeker coming from a neighbouring country is extremely restricted, to the point of being rather untenable," he said.

Fakhouri said the United Nations was currently sheltering a family of six Montagnards, who fled central Vietnam after bloody Easter Day clashes with authorities, in spite of efforts by the Cambodian army to stop them.

The family's arrival in Phnom Penh two weeks ago brings to 77 the number of mainly Christian Montagnards who have recently fled Vietnam and run a gauntlet of Cambodian troops and police intent on preventing them from seeking asylum.

Fakhouri said the husband and wife and their four children were shifted to Tuol Kok, a 10-minute drive from the UNHCR office.

"I felt that was unacceptable from a humanitarian perspective to maintain the family [at UNHCR] because they have been living for two weeks in the conference room of our office," Fakhouri told reporters at the end of his two-day mission in Cambodia.

Cambodia tightened border security in a bid to keep out refugees following the dispersal of thousands of demonstrating hill tribe people or Montagnards in Vietnam following bloody protests last month, circumventing a U.N. human rights convention signed by which it agreed to allow refugees into its territory

About 80 have now sought UNHCR protection, according to Cambodian authorities. Interior Minister Khieu Sopheak said at the weekend he believed at least some of the 80 had been smuggled into Cambodia in a bid to join relatives already settled abroad. The government recently alleged the UNHCR was secretly assisting Montagnards from the border to Phnom Penh.

Meanwhile, human rights activists and local media say Cambodian security forces have sent back Montagnards found to have crossed the border. One group of four was sent back last week, while local media say 160 Montagnards fled into Cambodia’s Mondulkiri Province last month but were arrested and deported.

In February 2001, Hanoi crushed a major uprising in the highlands over religious and property rights and has since then kept the area under tight control—with diplomats and reporters required to obtain clearance before visiting. A deluge of refugees fled across the border into Cambodia, with nearly 1,000 accepted into the United States as refugees.