The right group said the Vietnamese government had intensified a crackdown on the hill tribe, many of whom are members of unofficial churches. Government officials had broken up religious gatherings and forced people to renounce their faith, it said.

Communist Vietnam only allows religious groups sanctioned by the state.

Since 2001, at least 25 Montagnards have died in prison or shortly after being released from police custody. More than 250 are currently in jail or awaiting trial, the report said.

'Montagnards face harsh persecution in Vietnam, particularly those who worship in independent house churches, because the authorities don't tolerate religious activity outside their sight or control,' said Phil Robertson, deputy Asia director of Human Rights Watch.

The US government lifted the designation of Vietnam as a country of particular concern in 2006 after Vietnam passed legislation outlawing forced renunciations and permitting the official recognition of new denominations.

Deutsche Presse Agentur - March 31, 2011