Protests led by Buddhist monks against Chinese rule in Tibet turned violent Friday, bathing Lhasa in smoke from tear gas, bonfires and burned shops, and posing a challenge to China on whether its image can withstand a harsh crackdown ahead of the Beijing Olympics.

At least 10 people died in the rioting, state media reported.

From exile in India, the Dalai Lama appealed to China not to use force to end the largest, most sustained demonstrations in nearly two decades against Beijing's 57-year rule in Tibet. China's government in Tibet accused the Dalai Lama's supporters of inciting the unrest and imposed a curfew, ordering people to stay indoors.

Eyewitness accounts and photos posted on the Internet portrayed a chaotic scene in Lhasa, the provincial capital, with crowds hurling rocks at security forces, hotels and restaurants. The U.S. Embassy said Americans had reported gunfire.

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Reports of deaths varied and could not be independently verified, but China's official Xinhua News Agency said Saturday that 10 people were confirmed dead. The dead included "business people," according to an earlier Xinhua report. The agency also has said no foreigners were hurt.

At a demonstration outside the United Nations in New York, Psurbu Tsering of the Tibetan Association of New York and New Jersey said its members received phone calls from Tibet claiming 70 people had been killed and 1,000 arrested.

In some of the strongest words yet from officials, regional Tibet government head Champa Phunstok warned Saturday that the authorities will respond forcefully.

"We did not open fire, however we will deal harshly with these criminals who are carrying out activities to split the nation," he told The Associated Press on the sidelines of the National People's Congress in Beijing, China's annual legislative session.

Shops were set on fire Friday along two main streets surrounding the Jokhang temple, Tibet's most sacred shrine and the heart of Lhasa's old city, sending out thick clouds of smoke. Young men set fire to a Chinese flag and a huge bonfire burned in a street. Armed police in riot gear backed by armored vehicles blocked intersections, said a Tibetan guide.

The violence, which came on the fifth day of sporadic and largely peaceful protests, poses difficulties for a communist leadership that has looked to the Aug. 8-24 Olympics as a way to recast China as a friendly, modern power. Too rough a crackdown could put that at risk while balking could embolden protesters, costing Beijing authority in often restive Tibet.

"China is afraid of letting this protest mount. On the other hand, the world's eyes are upon China in advance of the Olympics. If they're too heavy-handed, it could cause them a lot of problems," said Jamie Metzl of the New York-based Asia Society. "It's an open question as to how much China thinks it can afford a major crisis in advance of the Summer Olympics."

On Saturday, Xinhua said Lhasa had "reverted to calm at the wee hours" and electricity and phone service, which had been cut for parts of Friday, was being restored.

Witnesses said police were patrolling the streets but things appeared peaceful. Shops were closed but government staff were required to work, said a woman who answered the telephone at the Lhasa Hotel.

"There's no conflict today. The streets look pretty quiet," said the woman who refused to give her name for fear of retribution.

On Friday, in an ominous turn for Beijing, the street protests broadened. Photographs taken by camera phone and provided by the Indian branch of Students for a Free Tibet showed hundreds of Tibetans marching through Xiahe, a Tibetan town in the western province of Gansu. Robed monks displayed the banned Tibetan national flag.

In Lhasa, the protests that had largely been confined to monks spilled over to ordinary Tibetans, who vented pent-up anger at Chinese and their businesses. Guests and employees at the Lhasa Dong Cuo International Youth Hostel huddled in the lobby, away from windows being smashed by protesters.

"Monks and very young men down to the age of 15-16 are smashing the Chinese shops, kicking in doors and windows, setting the shops on fire and beating the Chinese in the vicinity," the Danish daily Politiken quoted an unidentified witness as saying.

The exiled Dalai Lama, whom most Tibetans consider their spiritual leader, said China should stop using force in Tibet, saying he is "deeply concerned."

"I therefore appeal to the Chinese leadership to stop using force and address the long-simmering resentment of the Tibetan people through dialogue with the Tibetan people. I also urge my fellow Tibetans not to resort to violence," he said in a statement released in Dharmsala, India, seat of the government-in-exile.

Actor Richard Gere, a Buddhist who has spoken out for Tibetan independence since 1978, said he was not surprised by the uprising.

"You can't repress the people to the extent that Tibetans have been repressed for the last six decades now and not expect that at some point that it will explode," he told The Associated Press.

As in Myanmar, where Buddhist monks led pro-democracy protests in September, Buddhism permeates every aspect of Tibetan life.

Over the centuries, Tibet was at times part of China's dynastic empires. Communist forces invaded the region in 1950, to reclaim the Himalayan region and seize the commanding heights overlooking rival India. Pressured to cede more power to the communists, the Dalai Lama fled into exile in 1959 after a failed uprising.

The latest unrest began Monday, the anniversary of the 1959 rebellion, when 300 monks from one monastery demanded the release of other monks detained last fall. But political demands soon came to the fore. Other monks and ordinary Tibetans demanded independence and unfurled the Tibetan flag. Arrests ensued, leading to more protests.

Friday's violence apparently was triggered after police moved in to stop a group of protesting monks. Crowds then grew, and when police showed up in larger numbers, protesters attacked police cars and shops.

"It was chaos everywhere. I could see fires, smoke, cars and motorcycles burning," said the Tibetan guide, who asked not to be identified for fear of government retaliation.

Xinhua issued terse reports in English only, saying people had been hospitalized with injuries and vehicles and shops burned. Hospitals contacted in Lhasa said they were ordered not to release any information.

The Tibet government called the riot an act of sabotage that was "organized, premeditated and masterminded by the Dalai clique," according to Xinhua.

The unrest came as Tibet, long China's poorest province, has wracked up stunning growth, in part fueled by hefty investment and subsidies from Beijing meant to alleviate resentment among Tibetans. Still, Tibetans have complained that the economic benefits have mainly enriched Chinese, many of them newcomers, leaving Tibetans feeling more marginalized.

China, which has invested billions of dollars in Olympics preparations, has staked its national prestige on the games. Five months before the games begin, it had expected to bask in international praise. Instead, the protests are attracting the kind of international attention China doesn't want.

The White House urged China to "respect Tibetan culture," while the U.S. ambassador to China urged senior Chinese officials to use restraint in dealing with the protesters, according to State Department Spokesman Sean McCormack.

"Beijing needs to respect Tibetan culture. ... We regret the tensions between the ethnic groups and Beijing," said White House spokesman Gordon Johndroe. President Bush "has said consistently that Beijing needs to have a dialogue with the Dalai Lama."

European Union leaders also appealed to China to show calm in Tibet, but released a statement condemning China's handling of the protests so far.

Other Tibet watchers are less certain that international scrutiny will hold back China's hand if it feels threatened.

"Chinese leaders are not afraid of using force when they feel it's necessary. I don't think they'll be shy because there's now been violence on the demonstrators' side. I feel they think this gives them the green light to use a strong response," said Robbie Barnett, a Tibetan studies expert at Columbia University.

U.N. High Commissioner for Human Rights Louise Arbour issued a statement expressing concern "about escalating tensions."

International Olympic Committee President Jacques Rogge declined to comment on the protests. But speaking generally about China, Rogge said the human rights issues were not the focus of his group. "We are not an activist organization."

Tibet has been a focal point for protests by activists and international supporters ahead of the start of the Olympic torch relay, scheduled to come through China in May. Beijing plans for the torch to be carried to the top of Mount Everest, and closed its side of the mountain to climbers in a bid to prevent activists from disrupting the relay.

The timing of the Olympics has been a key factor for pro-independence advocates, said Kate Saunders, with the International Campaign for Tibet.

"There's an awareness in Tibet of the international spotlight on China and of the way that groups outside and individuals from different organizations are actively using the global spotlight to press for change in China," she said.