Beijing  - Two Tibetan women were arrested for staging separate protests that were critical of China in the south-western Chinese province of Sichuan, an advocacy group for Tibet said Saturday.

A nun in her 20s and a 36-year-old woman were detained Thursday in Ganzi, a Tibetan area of Sichuan, after handing out pamphlets that called for the exiled Dalai Lama's return to Tibet, respect for Tibetans' human rights, religious freedom and the release of Tibetan political prisoners, the International Campaign for Tibet said.

Their whereabouts are unknown, it added.

The organization said the arrests occurred "in an atmosphere of increasing tension in the area" ahead of the 50th anniversaries of the March 10, 1959, start to a failed Tibetan uprising against Chinese rule and the March 17, 1959, flight of the Dalai Lama into exile in India.

Rallies held last year on the March 10 anniversary escalated in Lhasa days later into anti-Chinese violence, the worst in almost two decades. The protests spread to other Tibetan-settled areas, including Ganzi.

Nearly 1,000 Tibetans were arrested in Lhasa over last year's unrest and 76 received prison terms ranging from less than five years to life, said Qiangba Puncog, the chairman of the Tibet Autonomous Region. The remainder were released, he said, according to the official China Daily newspaper.

Most of those convicted were found guilty of theft, robbery, arson, disrupting public services or attacking government agencies while a few were found guilty of "endangering national security," Puncog said Friday in Beijing.

No information was given for arrests made last year in other parts of Tibet or the neighbouring provinces of Sichuan, Qinghai and Gansu.

He said he did not expect unrest on this year's anniversary.

He said no unusual security measures were being taken, but Tibet activists said China has placed Tibet under "de-facto martial law" ahead of the anniversaries.

Witnesses in Tibet reported a strong army presence, military convoys, deployment of paramilitary police and roadblocks, the London-based Free Tibet Campaign said Friday.

"I cannot swear that some individuals won't make reckless moves next week, but riots like those seen last March won't happen again," Puncog said. (dpa)