BEIJING — A Tibetan nun killed herself Monday by setting herself on fire in a Tibetan town in western China while calling for religious freedom and the return of the Dalai Lama, the exiled Tibetan spiritual leader, according to a statement by an advocacy group based in London.

The nun, Tenzin Wangmo, 20, was the ninth Tibetan to commit self-immolation since March, the fifth of those to die, and the first Tibetan woman to kill herself in this way, said the group, Free Tibet. The self-immolations have all taken place in restive Tibetan areas of Sichuan Province. All the previous acts involved monks or former monks; the most recent one took place on Saturday, when a 19-year-old former monk from Kirti Monastery set himself on fire but lived.

Kirti is in the town of Aba, known as Ngaba in Tibetan, and is the focal point of a long-running repression by Chinese security forces. Kirti was involved in the widespread Tibetan uprising of 2008, and security around the monastery has tightened considerably since then. Seven of the eight monks who committed self-immolation this year came from Kirti.

Tenzin’s nunnery, called Dechen Chokorling, was just three kilometers outside Aba and near Kirti. Tenzin set herself on fire outside the nunnery around 1 p.m. on Monday, said the report by Free Tibet, which advocates for Tibetan independence and has functioned as an outlet for people inside the Tibetan areas to report news.