LHASA, China - Police closed off Lhasa's Muslim quarter on Friday, two weeks after Tibetan rioters burned down the city's mosque amid the largest anti-Chinese protests in nearly two decades.

Officers blockaded streets into the area, allowing in only residents and worshippers observing the Muslim day of prayer. A heavy security presence lingered in other parts of Lhasa's old city as clean-up crews waded through the destruction inflicted when days of initially peaceful protests turned deadly on March 14.

It was not clear why the area was cordoned off, although rioters had prominently targeted businesses belonging to Chinese Muslim migrants known as Hui, who control much of Lhasa's commerce.

The protests were the longest and most-sustained challenge to China's rule in the Himalayan region since 1989. The ensuing crackdown by Chinese authorities has focused international attention on China's human rights record in the runup to the Olympic Games.

China has faced growing calls from the United States and other countries to open a dialogue with the Dalai Lama, Tibet's exiled spiritual leader, along with suggestions from some leaders that they were considering boycotting the Olympics' opening ceremony in protest at Beijing's handling of the Tibetan situation.

Apparently as a result of the pressure, the Foreign Ministry is allowing a group of foreign diplomats to visit Lhasa on Friday and Saturday, including a U.S. diplomat.

A small group of foreign journalists, including an Associated Press reporter, was taken to Lhasa earlier in the week on a three-day government-organized trip that ends Friday.

The otherwise tightly scripted visit was disrupted when 30 red-robed monks pushed into a briefing being given by officials at the Jokhang Temple on Thursday, complaining of a lack of religious freedom and denouncing official claims that the Dalai Lama orchestrated the March 14 violence.

"What the government is saying is not true,'' one monk shouted out.

"They killed many people. They killed many people,'' another monk said, referring to Chinese security forces.

The outburst by the monks lasted for about 15 minutes before government officials ended it and told the journalists it was "time to go.''

China has strenuously argued that the widespread arson and looting were criminal acts orchestrated by separatists, while refusing to discuss the root causes of the anger and alienation blamed for sparking the violence.

A vice-governor of Tibet, Baima Chilin, later told reporters the monks would not be punished.

However, Tibet activists on Friday, voiced concern over possible Chinese government retaliation against the Buddhist monks.

"There are serious fears for the welfare and whereabouts'' of the monks, the International Campaign for Tibet said in a statement.

Other than the incident at the Jokhang, one of Tibetan Buddhism's holiest shrines, most of the second day of the tour went according to plan, with officials sticking to the government line that the most violent anti-Chinese protests in nearly two decades were plotted by supporters of the Dalai Lama.

The Dalai Lama has denied the accusations and threatened to resign as head of the India-based Tibetan government-in-exile if the violence continued.

The protests had initially started out peacefully among monks in Lhasa on March 10, the anniversary of a failed 1959 uprising against Chinese rule. But four days later, they spiralled into violence. Tibetans torched hundreds of buildings and attacked members of China's dominant Han ethnic group and Chinese Muslims known as Hui, who have dominated commerce in the city.

A staffer at the China Tibet Information Center said there were approximately 1,500 Muslims in Lhasa. Officials with the Lhasa government and Religious Affairs Bureau said they did not know how many Muslims were in Lhasa.

The government says at least 22 people have died in Lhasa; Tibetan rights groups say nearly 140 Tibetans were killed, including 19 in Gansu province.

One of the monks protesting Thursday said the death toll was far higher than the government was saying, but did not give the source of his information.

"The cadres and the army killed more than 100 Tibetans. They arrested more than a thousand,'' he said.

After the violent 1989 uprising in Lhasa, Tibetans claimed many more Tibetans died than the official toll of 16 because families feared punishment if participants went to hospitals.

Fu Jun, head of the News Affairs Office of the Propaganda Department of the Tibet Communist party, said Friday the monks were spreading rumours.

"We are keeping an open mind about their complaints. The rumour is misleading the media without a shred of evidence ... We will clear up facts in a few days time when appropriate,'' Fu said.

Journalists were taken Friday morning to interview members of the Communist party-run Buddhist Association, who reiterated standard Chinese accusations against the Dalai Lama.

"This was premeditated,'' said Drubkang, a reincarnated lama and member of Beijing's top government advisory body, who like many Tibetans uses just one name.