A Tibetan man is in critical condition after setting himself on fire in Nepal on Wednesday, police said, the 100th self-immolation bid since 2009 according to a toll by Tibet's exiled government.

Police spokesman Keshav Adhikari told AFP that the exile doused himself in petrol and set fire to himself in a restaurant at Kathmandu's Boudhanath Stupa, one of the world's holiest Buddhist shrines.

"At around 8:20 am (0235 GMT) a man in his early 20s arrived at a restaurant on the premises of the Boudhanath Stupa. He went straight to the toilet and poured petrol over his body and set himself alight," he said.

A small number of tourists who were eating breakfast began screaming for help, Adhikari added, and police patrolling nearby were alerted.

"The policemen doused the flames and sent him to hospital. He is in a critical condition. His entire body was caught in the flames. At the hospital he tried to speak but couldn't," Adhikari told AFP.

The officer said it was not yet clear if the man had been shouting slogans protesting against China's rule in the Himalayan region of Tibet when he set himself alight.

The Tibetan government in exile, based in the Indian town of Dharamshala, had previously said that 99 Tibetans had set themselves alight, with 83 of them dying as a result of their injuries.

It attributes the protests to a growing sense of desperation in Tibet over Chinese rule.