BEIJING — An 18-year-old Tibetan nun has set herself on fire in western China in the latest such protest against Beijing's handling of the vast ethnic Tibetan regions it rules, an overseas activist group said Sunday.

Free Tibet said in a statement that the nun set herself ablaze Saturday and was believed to have survived. The young woman, identified as Tenzin Choezin, was a nun at the Mamae Nunnery in Sichuan province's Aba prefecture, the statement said.

It said Choezin shouted slogans of protest against the Chinese government before setting herself on fire at a junction close to the nunnery.

"Soldiers and police came immediately and took her away," the statement said. "Soldiers then surrounded the nunnery and sealed it off."

As many as 18 monks, nuns and ordinary Tibetans have set themselves on fire over the past year, and Free Tibet says at least 12 died from their injuries.

Activist groups say the self-immolations are a protest against China's policies and a call for the return of the Dalai Lama, the Tibetans' spiritual leader who fled from the Himalayan region to India amid an abortive uprising against Chinese rule in 1959.

Government and police officials reached by telephone in Aba said they knew nothing about any self-immolation and hung up. There was no number publicly listed for the nunnery.

A statement by two Tibetan monks exiled in India, Losang Yeshe and Kanyag Tsering, distributed by the London-based International Campaign for Tibet said Choezin was the eldest of four children and a good student.