The Tibetans, from China's western Gansu province, were arrested in May 2005 for passing out letters calling for independence for Tibet, the London-based Free Tibet Campaign said in a statement seen by Reuters on Tuesday.

"Three Buddhist nuns and two monks (were) sentenced following calls for no Beijing Olympic Games until the Tibet issue is peacefully resolved," it said.

The five were jailed for terms stretching from 18 months to three years.

Tibet has been under Chinese control since 1950, when the People's Liberation Army marched into the vast, mountainous area.

China calls Tibet an "autonomous region", but critics say that Tibetans enjoy no real autonomy and that Buddhist monks and nuns loyal to the region's exiled gold-king, the Dalai Lama, have been jailed and tortured.

The Dalai Lama, who fled to India after a failed uprising in 1959, has renounced the goal of an independent Tibet and says he only wants more autonomy.

China accuses him of continuing to spark separatist efforts among the 2.7 million Tibetans and refuses to allow him back inside its borders.

Overseas activists have previously urged the International Olympic Committee to warn China its right to host the 2008 Games could be revoked if it does not improve its human rights record.