Ten more Tibetans are reported to have been arrested in connection with a bombing campaign in south-west China, which saw two other Tibetans sentenced to death last month.

This information raises serious concerns... about the apparently widening scope of this case Mary Beth Markey, International Campaign for Tibet

The case caused an international outcry when it was reported in December.

It was not clear when the group of 10 were arrested. The two who were sentenced last month were detained in April.

A Chinese official confirmed that of the group of 10, three had been sentenced, the Associated Press news agency reported.

"This information raises serious concerns, about these 10 additional arrests, about the apparently widening scope of this case, and about the possibility that China may have withheld this information in recent human rights talks," said Mary Beth Markey, executive director of the International Campaign for Tibet's Washington office.

Plea of innocence

One of the Tibetans who was sentenced in December, Tenzin Deleg Rinpoche, smuggled a tape proclaiming his innocence out of jail, a US government-financed radio network reported on Wednesday.

"I am completely innocent," Radio Free Asia quoted him as saying.

"I was wrongly accused because I have always been sincere and devoted to the interests and well-being of Tibetans," it quoted the monk as saying. "The Chinese did not like what I did and what I said. That is the only reason why I was arrested."

Tenzin Deleg Rinpoche's death sentence was suspended for two years. Correspondents say such sentences are usually commuted to life imprisonment.

Restive area

The three Tibetans whose fate was reported on Wednesday were sentenced in two separate trials in the Ganzi district of Sichuan, western China, an official from the local religious affairs bureau told AP on condition of anonymity.

The town of Ganzi has faced repeated crackdowns by Chinese police trying to root out pro-independence activists.

The area has a majority ethnic-Tibetan population and has long been a hotbed of pro-Tibetan independence activity.

The official said the defendants were linked to Lobsang Dhondrup, sentenced to death last month, who was found guilty of three attacks in Sichuan, one of which killed a bystander.

China has long accused Tibetan pro-independence activists of a campaign of violence against Chinese targets.

But the BBC's Rupert Wingfield-Hayes, in Beijing, says details of actual incidents rarely get reported.

Western Sichuan was originally known as Cham and was historically part of Tibet.

After the Communists came to power in China in 1949, they amalgamated Cham into Sichuan province.

In 1951, China's People's Liberation Army invaded and occupied the rest of Tibet.