BEIJING - Rock-throwing protests erupted yesterday in Tibet's capital, Lhasa, and fires were set as unrest over Chinese rule of the autonomous region escalated to its highest level in two decades.

Witnesses reported random gunfire and looting in the city and said angry Tibetans were chasing down and beating Chinese in the streets.

At least seven people died, state media reported.

By evening, authorities had ordered a curfew and stationed thousands of police officers with riot shields, backed by armored vehicles, around the city.

Security forces set up a cordon around a monastery after lockdowns at three others where crimson-robed monks had begun protest marches earlier in the week.

The unrest presents a major challenge to China in the months before the Beijing Summer Olympics in August as it tries to project an image of a modern, less-repressive state.

The Tromzikhang market, a flagship building in the old city of Lhasa, burned during much of the day, witnesses said. Elsewhere, "a number of shops were burnt," China's state-run Xinhua news agency said in a brief dispatch.

Protesters set tires afire in various parts of the city and smashed and torched police cars and fire trucks, witnesses said.

Security forces appeared to be using restraint in dealing with the unrest, even amid reports that ethnic Tibetans in neighboring Gansu and Sichuan provinces were joining the revolt.

The U.S. Embassy warned Americans to stay away from Tibet, noting firsthand reports from U.S. citizens in the city of "gunfire and other indications of violence."

Internet accounts painted a picture of chaos in Lhasa, a city of 300,000 people more than two miles high on the remote Tibetan plateau.

"People were just running about randomly. Some of them were looting," said a witness who used the Internet name "North Wind" on the fanfou.com Web site.

The Tibetan Center for Human Rights and Democracy, a nonprofit advocacy group in Dharamsala, India, said that roads in and out of Lhasa had been closed.

The unrest in Lhasa began Monday and Tuesday when hundreds of monks left their monasteries and took to the streets in an unusual, peaceful display of opposition to Chinese rule of Tibet. The monks were marking the 49th anniversary of a failed uprising that forced the Dalai Lama, Tibet's spiritual leader, to flee into exile in India.

In a coordinated series of uprisings by Tibetan exiles, similar protests also occurred in Kathmandu, Nepal and near Dharamsala, where the Dalai Lama maintains a government in exile.

By yesterday, the protests in Lhasa had evolved into attacks by ordinary Tibetans on ethnic Han Chinese, who run many of the shops and markets in old Lhasa.

Han Chinese, who make up 92 percent of China's population of 1.3 billion people, have migrated to Tibet in great numbers this decade, leading Tibetans to complain of a dilution of their culture and identity.

Han Chinese shopkeepers near the central Jokhang Temple, one of Tibetan Buddhism's holiest sites, said the day's events terrified them.

"I've been trapped for three or four hours," An Li, the 28-year-old proprietor of the Lhasa Donkey Pot restaurant, said by telephone. "I don't dare go out. The windows of my restaurant were smashed . . . at 10 this morning."

"They [Tibetans] are searching for Han people from one shop to the next, and smashing every shop of theirs," she said. "I'm wondering why police don't yet come."

Tibetan advocates abroad said the anger in Tibet should not come as a surprise.

"Tibetans feel increasingly marginalized in their own country. The Tibetan plateau is being flooded [with Han Chinese], and this could spell the end of Tibetan culture and identity," said Matt Whitticase of the London-based Free Tibet Campaign, an advocacy group.

The U.S. government-funded Radio Free Asia said some monks from the Sera Monastery in Lhasa were on a hunger strike, demanding that Chinese paramilitary forces withdraw from the monastery compound. It also said two monks from the Drepung Monastery were in critical condition after attempting suicide by cutting their wrists.

Mt. Everest To Be Off-Limits For Olympic Torch-Carrying

There are two routes

to scale Mount Everest, the world's highest peak. Both will be off-limits to mountaineers this spring, as China strives to carry the Olympic torch over Everest and inaugurate the summer Olympic Games free of pro-Tibetan protests.

China announced

earlier this week that the route along the north face of the mountain, in Chinese-controlled Tibet, would be closed. Yesterday, Nepal's tourism minister said his country would heed a Chinese request to not allow climbers on the south face of the mountain, in Nepal, at least between May 1 and May 10.

China's plans

to have the Olympic torch carried into Tibet over Everest have drawn protests from groups that advocate greater autonomy for Tibet, including among monks in Tibet's capital, Lhasa.

- New York Times News Service

This article includes information from the Associated Press.