Journalists described Lhasa as a divided city
Foreign diplomats are in Tibet on a fact-finding visit approved by China, following criticism of Beijing's crackdown on Tibetan protests.
The UK and the US are among the 15 nations invited on the one-day trip to Tibet's capital Lhasa - the first since anti-China riots began two weeks ago.
The US welcomed the move, but said diplomats and observers should be allowed to see areas surrounding Lhasa.
The visit follows a short trip to the city by a group of foreign journalists.
Meanwhile, European Union foreign ministers meeting in Slovenia have rejected a proposed boycott of the opening ceremony of the Olympic Games in Beijing.
European leaders have been among the most vocal in criticising China's reaction to the protests in Tibetan communities.
Tibet's government-in-exile, based in India, says about 140 people were killed in a crackdown by Chinese security forces. Beijing disputes this, saying 19 people were killed by rioters.
A group of 17 diplomats from countries including Japan and Australia arrived in Tibet from Beijing on Saturday.
They are expected to return to the Chinese capital later on Saturday.
US state department spokesman Sean McCormack said the trip was a "step in the right direction".
"But it's not a substitute for the ability of our diplomats, as well as others, to travel not only to Lhasa, but into the surrounding area specifically," he said.
The visit follows a short trip by a group of journalists from Chinese and international media.
A 30-strong group of monks in Lhasa staged a noisy protest as the reporters were shown around one of Tibet's holiest sites, the Jokhang Temple, on Thursday.
The monks shouted "Tibet is not free, Tibet is not free".
Associated Press reporter Charles Hutzler said the outburst was the only spontaneous moment in an otherwise tightly controlled trip.
A Tibetan exile group expressed fears for the "welfare and whereabouts" of the monks involved in the outburst, but Chinese officials insisted no action would be taken.
"We will never do anything to them," the vice-governor of Tibet, Baima Chilin, told reporters on the trip.
"We will never detain anyone you met on the streets of Lhasa. I don't think any government would do such a thing."
The reporters described Lhasa as a divided city - with Chinese areas resuming normal business, but the old city, mainly populated by Tibetans, still under a heavy police presence.
The BBC's request to take part in the media trip was turned down.
Western media organisations are still prevented from reporting freely in the area.
Tibet's spiritual leader, the Dalai Lama, has once again appealed for China's leaders to engage in "meaningful dialogue" over the issue.
Officials have frequently blamed the Dalai Lama for the protests. He denies encouraging violence.
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