Six hundred Tibetans are reported to have been detained by Chinese security forces in the capital Lhasa after two people set themselves on fire on Sunday.
The BBC reports one of the men has died from his injuries. The incident took place outside the Jokhang temple.
Xinhua news agency reported that both were Tibetans from outside Tibet.
The Tibetan Centre for Human Rights and Democracy in Dharamsala said the temple had since been closed to foreigners and pilgrims.
Rights groups says at least 35 people have set themselves on fire since March last year in protest against China's six-decade rule over Tibet. At least 27 have died.
Radio Free Asia, an American broadcaster, says about 600 Tibetans have been detained since the weekend.
But the number cannot be independently confirmed because foreign journalists are barred from entering Tibet.