BEIJING (Reuters) - China gave Tibetan independence protesters an ultimatum to surrender on Saturday after riots in Lhasa which killed at least 10 people in the worst unrest in the region for two decades.

The tough response by the Chinese authorities came after fierce protests on Friday which contradicted China’s claims of stability and tarnished a carefully-nurtured image of national harmony as it readies to stage the Olympic Games in August.

Official Tibetan judicial authorities gave protesters until Monday night to turn themselves in and benefit from leniency.

“Criminals who do not surrender themselves by the deadline will be sternly punished according to the law,” said a notice on the Tibetan government Web site (www.tibet.gov.cn).

International pressure mounted on Beijing to show restraint. Australia, the United States and Europe urged China to find a peaceful outcome, while Taiwan, which China claims as its own, predictably condemned Beijing for launching a crackdown.

Xinhua news agency said 10 “innocent civilians” had been shot or burned to death in the street clashes in the remote, mountain capital which has been sealed off. The dead included two people killed by shotguns.

Xinhua said 12 police officers had been “gravely injured” and 22 buildings and dozens of vehicles were set on fire.

A source close to the Tibetan government-in-exile, however, questioned the official death toll of 10. He said at least five Tibetan protesters had been shot dead by troops.

Some Tibet monitoring organizations outside the country put the death toll at up to 32.

The riots emerged from a volatile mix of pre-Olympics protests, diplomatic friction over Tibet and local discontent with the harsh ways of the region’s Communist Party leadership.

The protests, the worst since 1989 in the disputed region, have thrust China’s role as Olympic host and its policy towards Tibet back into the international spotlight.

A rash of angry blog posts appeared after the deaths were confirmed. Hollywood actor Richard Gere, a Buddhist and an activist for Tibetan causes, urged an Olympics boycott.

Official statements suggested the government reaction in coming days would be tough, with Tibetan Buddhist monasteries -- traditional focal point of opposition to Beijing’s rule -- and nunneries being brought under tighter control.

PUNISHMENT AND REWARDS

The regional communist-controlled government said those who harbored protesters would be punished and offered rewards and protection to informers. Tibet television urged residents to denounce the “malicious intent” of the Dalai Lama.

Tibetan crowds in Lhasa attacked government offices, burned vehicles and shops and threw stones at police in Friday’s confrontations. Many people were injured.

Chinese television showed footage of rioters trashing shops and trying to break down the entrance of a bank, and plumes of smoke floating above the city.

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A Reuters picture showed a protester setting on fire a Chinese national flag. Another depicted security personnel shielding themselves against rocks hurled by protesters.

Qiangba Puncog, the top government official in Tibet, told reporters in Beijing that Tibetan authorities had not fired any shots to quell the violence.

John Ackerly, of the International Campaign for Tibet, said in an e-mailed statement he feared “hundreds of Tibetans have been arrested and are being interrogated and tortured”.

Hundreds of angry young Tibetans protested on Saturday in Dharamsala, home to Tibet’s exiled spiritual leader the Dalai Lama and the refugees’ “government-in-exile”.

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Not far from where the Dalai Lama was recovering from a cold and keeping up his lifetime routine of praying for peace, the crowd of young Tibetans gathered to vent their rage.

The crowd tore apart a flaming effigy of Chinese President Hu Jintao in normally peaceful Dharamsala in the Indian Himalayas and the protesters decided to march to New Delhi.

A Western tourist said that Lhasa itself was like a ghost town on Saturday, though it was packed with Chinese soldiers.

China has accused followers of the Dalai Lama of engineering unrest in the run-up to the Beijing Olympics. The Olympic torch relay will pass through Tibet in a few weeks time.

Although the Dalai Lama was resting after falling ill with a cold, he released a statement condemning the “brute force” of China on Friday and will meet with journalists on Sunday.

“He is a monk so he follows his routine,” explained Chhime Chhoekyapa, the Dalai Lama’s spokesman. That includes listening to news on the radio. “He said it’s very sad,” said Chhoekyapa. “As a Buddhist he prays for peace.”

The Free Tibet Campaign organization cited eyewitnesses as saying that thousands marched on government buildings in Xiahe, an ethnic Tibetan area of China, and raised a Tibetan national flag at a school.

In Lhasa, Danish tourist Bente Walle, 58, said: “Today Lhasa is completely closed and there is Chinese military all over.”

(Additional reporting by Guo Shipeng, Nick Mulvenney, Ben Blanchard and Lindsay Beck in Beijing, John Ruwitch in Chengdu and Sophie Taylor in Shanghai)