Human Rights Watch condemned Vietnam for its "repression" of ethnic minority Christian Montagnards in the Central Highlands following bloody clashes with security forces, and called for international observers to be given immediate access to the region.
The New York-based organization also urged Cambodia to honor its obligations under the United Nations Refugee Convention and to stop forcing back to Vietnam those Montagnards fleeing the crackdown by the Vietnamese authorities.
"The human rights situation for Montagnards in the Central Highlands has plummeted to a new low," Brad Adams, executive director of the Asia Division of Human Rights Watch, said in a statement.
"Vietnam's policy of repression of Montagnard Christians is only fueling the unrest."
The watchdog said thousands of Montagnards attempted Saturday to enter Buon Ma Thuot, the capital of Dak Lak province, to conduct five days of protests against religious persecution and confiscation of ancestral lands.
Clashes erupted when police used tear gas, electric truncheons, and water cannons to prevent the demonstrators from entering the city, arresting dozens of people, according to Human Rights Watch.
The group said it had received eyewitness reports of protestors being beaten to death by security forces outside Buon Ma Thuot, as well as unconfirmed reports of police casualties.
On Easter Sunday, Montagnards in Gia Lai province demonstrated in many districts near their villages because police blocked them from protesting in the capital, Pleiku, it said, adding that people were beaten and arrested.
"Since last weekend, dozens, if not hundreds, of Montagnards are missing. Many Montagnards did not return to their villages after the demonstrations, knowing that police were there, ready to make arrests," the organization said.
"Others have been arrested and their current whereabouts are unknown. Some may be wounded or dead."
Adams expressed concern that those being held by the police could face torture and mistreatment and urged access for independent observers.
Vietnamese foreign ministry spokesman Le Dung rejected the allegations as "ill-willed fabrication and exaggeration," insisting that "Vietnamese laws guarantee the right to freedom of religion and beliefs".
"I would like to repeat that all aspects of life in the Central Highlands remain normal," he said.
The ministry, however, has so far refused requests by AFP to visit the impoverished region.
Visits by diplomats and foreign journalists to the Central Highlands are tightly controlled. On Saturday a delegation of US diplomats were prevented by police from travelling to Buon Ma Thuot by car.
The latest clashes were the first large-scale demonstrations in the region since February 2001 when security forces forcibly broke up protests by more than 20,000 Montagnards, triggering a mass exodus into Cambodia.
According to the watchdog, the Vietnamese government has increased its persecution of Montagnard Christians this year, particularly those thought to be following evangelical "Dega Protestantism," which is outlawed.