Hundreds of people have been detained in Lhasa after two men set themselves on fire in the Tibetan regional capital on Sunday in protest against Chinese rule, a US-based broadcaster reported.

Radio Free Asia said Chinese security forces had rounded up hundreds of residents and pilgrims in the wake of the immolations, the first significant protest in the heavily guarded city since deadly anti-government riots in 2008.

It quoted a local source as saying about 600 Tibetans had been detained and those from outside the Tibet Autonomous Region (TAR) had been expelled.

At the time of the protest, Lhasa was filled with Tibetan Buddhist pilgrims who had travelled to the city to celebrate Saga Dawa -- the anniversary of Buddha's birth.

The two protesters, who were both from outside the TAR, set themselves on fire in front of the famed Jokhang Temple, a popular pilgrimage destination in the centre of Lhasa.

Police immediately put out the flames and one of the two men survived, according to state news agency Xinhua. His current whereabouts are not known.

Sunday's incident was the first of its kind in the Tibetan capital, which has been under tight security since deadly anti-Chinese government riots broke out there in 2008.

Residents of Lhasa said the city was under even tighter security than usual following Sunday's protest, with police and paramilitary officers out in force.

One resident contacted by AFP on Monday said police were carrying out identity checks in the streets and that mobile telephone signals had been blocked.

Free Tibet, a London-based campaign group, also said it had received reports that Tibetan residents in Lhasa had been arbitrarily detained in the wake of the protest.

More than 30 people have set themselves on fire in Tibetan-inhabited areas of China since the start of March 2011 in protest at what they say is religious and cultural repression by the Chinese authorities.

Tibetans have long chafed under China's rule over the vast Tibetan plateau, saying that Beijing has curbed religious freedoms and their culture is being eroded by an influx of Han Chinese, the country's main ethnic group.

Beijing insists that Tibetans enjoy religious freedom and have benefited from improved living standards brought on by China's economic expansion.