Tibet's government in exile, which is based in Dharamsala in India, said it had confirmed that Chinese authorities killed at least 30 Tibetans as they cracked down on the protests.
However, Thupten Samphel, a spokesman for the exiled government, told Al Jazeera that there were unconfirmed reports of a much higher death toll.
"We are hearing that over 100 people have been killed in the violence," he said.
"Over an extended period of time, there has been a blatant violation of human rights in Tibet. There have been restrictions on freedom of speech and freedom of thought.
"If China really wants calm restored to the country, it is in the best interests to engage in dialogue with the Dalai Lama, and other Tibetans in exile."
Government offices attacked
Government offices were attacked, vehicles and shops set on fire and stones thrown at police on Friday. Chinese television showed footage of rioters trashing shops and trying to break down the entrance of a bank.
Al Jazeera's Tony Cheng, reporting from Beijing, said the riots were a testament to the growing anger among the locals over what they call the "Chinese occupation of Tibet".
"People seem to have had enough of Chinese rule, and have expressed that on the streets of Lhasa," he said.
The communist-controlled regional government has blamed the Dalai Lama for the violence and on Saturday Tibetan television urged residents to denounce the spiritual leader's "malicious intent".
Qiangba Puncog, chairman of the Tibet autonomous regional government, claimed the protests were part of a "separatist" movement that authorities would not allow to succeed.
On Saturday, police with batons could be seen at checkpoints across the city and armoured personnel carriers drove along the streets, witnesses said.
"There are many armed police, special police and People's Liberation Army soldiers everywhere in the streets of Lhasa today," a Chinese resident said.
"I saw tanks and armoured personnel carriers patrolling the streets. They block every intersection to check vehicles."
Officials have warned that residents of Lhasa that harbour protesters will be punished and offered rewards and protection to informers.
Foreign tourists were told to leave, a hotel manager and travel guide told the Associated Press news agency, with the guide adding that some holidaymakers turned back at the airport.
|Tibetan exiles and their supporters held angry |
protests around the world [AFP]
The governor of Tibet, who was installed by China, told reporters that authorities would deal with rioters "harshly" and "calm will be restored very soon".