Tibetan monks have disrupted a tour by the first foreign journalists invited by China to visit Lhasa since protests erupted two weeks ago, witnesses say.
About 30 monks shouted pro-Tibetan slogans and defended the Dalai Lama as journalists toured the Jokhang Temple, an Associated Press reporter said.
China has accused the Dalai Lama of masterminding the protests.
But US President George W Bush has urged Beijing to begin dialogue with Tibet's exiled spiritual leader.
In a telephone conversation with counterpart Hu Jintao, Mr Bush raised concerns over the situation in Tibet and urged Beijing to ease access to the region for journalists and diplomats.
The protests began on 10 March and developed into violent rioting in Lhasa before spreading to neighbouring regions.
China says 19 people were killed by rioters. The Tibetan government-in-exile says about 140 people have been killed in a crackdown by Chinese security forces.
Foreign journalists have largely been blocked from covering the unrest, but on Wednesday China allowed a group of reporters into Lhasa for a three-day escorted visit. The group does not include the BBC.
The monks' protest came early on Thursday as they toured the Jokhang Temple - one of Tibet's holiest shrines.
One monk shouted "Tibet is not free, Tibet is not free" before he started to cry, an AP journalist at the scene reported.
Another monk said the rioting on 14 March "had nothing to do with the Dalai Lama".
Government handlers told the journalists to leave and tried to pull them away, the reporter said.
The group has also visited a medical clinic and a clothing store where Chinese authorities say five girls were trapped and burned to death, AP's reporter added.
A reporter for the London-based Financial Times, meanwhile, said that the Tibetan quarter of the city resembled a war zone, with burnt-out buildings, shuttered businesses and groups of soldiers on every corner.
The rioting appeared to have been more prolonged and destructive than previously thought, the reporter wrote.