Images of a man in monk's robes lying on the pavement as flames almost one meter (three feet) high engulfed him were posted on the website of Radio Free Asia (RFA), which is backed by the US government.
Yesterday's fiery protest, in Yushu, in the north-western province of Qinghai, was carried out by 26-year-old Sonam Topgyal, said the British-based campaign group Free Tibet.
"Information about whether he survived is not yet available," it said.
Phone and Internet communications were shut down immediately after the self-immolation attempt, and local people's movements restricted, Free Tibet said.
RFA said the burning was the sixth this year, and the 142nd such act in Tibet and elsewhere since 2009, most of them fatal.
Many Tibetans accuse the central government of religious repression and eroding their culture, as China's ethnic majority Han increasingly move into historically Tibetan areas.
Beijing condemns the self-immolation protests and also says it has brought development to Tibet. Yushu is a rugged, remote corner of the Tibetan plateau, where a devastating earthquake struck in 2010, killing nearly 2,700 people.