The woman self-immolated on Wednesday afternoon in front of a monastery in Barma township in the restive Aba region of south-western China's Sichuan province, London-based Free Tibet and other groups said.
Free Tibet identified the woman by the single name Rechok and said she was in her mid-30s. She died at the scene of her protest, it said.
"Barma Township is like many other places in Tibet," said Stephanie Brigden, the director of Free Tibet.
"People from all walks of life are rejecting Chinese rule and going to extraordinary lengths to make their calls for freedom heard," Brigden said.
Rechok's was the 38th self-immolation in Tibetan areas of China since 2009.
It follows similar protests by two young Tibetan men on Sunday in Lhasa, the capital of the Tibet Autonomous Region.
Police detained hundreds of people following the protests in Lhasa, questioning many local residents and expelling Tibetans whose homes were outside Lhasa, US-based Radio Free Asia quoted sources as saying.
Free Tibet said three of the previous self-immolations were in Barma township, adding that police shot dead another young Tibetan in Barma in January as he was trying to prevent the arrest of a friend who distributed leaflets supporting the protests.
The government has tightened security in most Tibetan areas this year after an escalation of the self-immolations and other protests, many of them by monks.
Chinese leaders accuse supporters of the Dalai Lama, the exiled Tibetan Buddhist leader, of encouraging the protests and pursuing independence for Tibet.
But the Dalai Lama has publicly opposed the self-immolations and said he seeks only greater freedom for Tibetans within China.Author: Bill Smith