BEIJING (Reuters) - Fresh rioting broke out in a Tibetan area of southwest China, defying a huge security crackdown there, even as officials in Tibet vowed swift, harsh punishment for those who sparked the initial anti-Chinese unrest.

Chinese security forces guard a street in Lhasa, Tibet April 1, 2008. The words on the signboard read, "Carry out duties in a civilized manner, maintain stability. Please cooperate with checks and thank you for your cooperation." REUTERS/Stringer

The latest riot to shake Tibetan areas of China occurred on Thursday night in Donggu Township, Ganzi (Garze) Prefecture, a largely ethnic Tibetan area in Sichuan province’s mountainous west, Xinhua news agency reported late on Friday.

“Police were forced to fire warning shots and put down the violence,” an official with the prefectural government said.

“An official was attacked and seriously wounded in a riot,” the brief report said, adding that he was “seriously wounded.”

The report did not explain the cause of the unrest or whether it involved ethnic Tibetans, who have been protesting against China’s rule and calling for the return of the exiled Buddhist leader, the Dalai Lama.

Ganzi and neighboring Aba in Sichuan province have seen torrid confrontation between Tibetan protesters and police in past weeks. Anti-riot troops have poured into the area.

A mob armed with stones and knives killed an armed Chinese policeman in Ganzi late last month. On March 16, Buddhist monks and residents in Aba protested, demanding Tibetan independence from China. More than 200 police and officials there were hurt when violence broke out, a local official said this week.

The widespread unrest began in Lhasa, the capital of neighboring Tibet province, and there officials on Friday vowed quick trials for those behind the unrest.

Lhasa was last month hit by Buddhist monks’ protests against Chinese rule that gave way to deadly rioting on March 14, and since then security forces have poured in to reimpose control there and in other restive Tibetan areas.

China says 19 people died in the Lhasa violence but representatives of the Dalai Lama say some 140 people died in the unrest across Tibet and nearby areas.

Chinese officials have accused the Dalai Lama of organizing the unrest to press for Tibetan independence ahead of the Beijing Olympic Games in August, and vowed to come down hard on rioters and on protesters supporting him.

The Dalai Lama has repeatedly denied the accusations and said he wants true autonomy, but not outright independence, for Tibet.

COURTS BACK CRACKDOWN

The region’s courts have made clear that they will back the crackdown, hand out tough verdicts and reinforce the government’s campaign against the Dalai Lama.

Tibet’s top law-and-order official Baima Chilin told judges to “use the weapon of the law to attack enemies, punish crime, protect the people and maintain stability,” the Tibet Daily reported.

“Use trial according to the law of all the criminals to shock criminality and root out the base of the separatists. Use ample evidence to expose to the world the Dalai clique’s lies of peace and non-violence.”

Baima Chilin ordered swift trials and said the judges “have the confidence of the Party.”

Slideshow ( 6 images )

On Thursday, an official Tibet news Web site (www.chinatibetnews.com) said police had caught over 800 people involved in the Lhasa violence and 280 people had turned themselves in. Monks involved in the earlier protests have also been charged.

The United States and many European countries have expressed worry about the tensions, calling on Beijing to open dialogue with the Dalai Lama, winner of the Nobel Peace Prize, and allow foreign reporters and observers to freely visit Tibet.

The United Nations High Commissioner for Human Rights, Louise Arbour, held “private discussions” with Chinese officials on Tibet and raised access to the region, her spokesman said on Friday.

“The issue of accessibility is obviously paramount because without that it’s very hard to come to any conclusions about what has happened or what should happen next,” Arbour’s spokesman Rupert Colville told a news briefing in Geneva.

But Chinese officials and state media have criticized Western news reports of the Tibetan unrest, claiming they have misrepresented violence as peaceful protest, vilified efforts to develop Tibet, and echoed false claims of independence advocates.

A major Chinese Internet site has now launched an online petition drive aimed at condemning Western media reports on the unrest.

By Friday evening, Sina.com’s online petition condemning Western press reports claimed close to one million signatures, with many signers voicing nationalist outrage.