According to London-based activist group Free Tibet, the monks called for freedom in Tibet and the return of the exiled spiritual leader, the Dalai Lama.
Another group, Free Tibet, said it had confirmed reports that a Tibetan woman was shot.
Harriet Beaumont, a spokeswoman for the advocacy group Free Tibet, identified the man who died as Dorjee Tseten, 19, from Bhora in Labrang County.
The advocacy group, Free Tibet, said three Tibetan men were shot, one fatally, by security forces outside a police station where the men had gone to protest.
One overseas activist group, Free Tibet, said its informants in Lhasa, the Tibetan capital, had reported a heavy increase in Chinese security forces there as well.
The advocacy group, Free Tibet, said in a statement that rumors were circulating in the region, known as Aba or Ngagba in Tibetan, that "many more people were prepared to give up their lives in protest".
The group, Free Tibet, said in a news release that the monk, Kalsang, set himself ablaze at 2 p.m. in a vegetable market in the town of Aba, known in Tibetan as Ngaba.
Last Monday, the London-based advocacy group Free Tibet said, Chinese forces killed at least one person and wounded at least 34 in Luhuo, or Draggo, a monastery town west of Chengdu.
A few days before his death, Shichung had complained to friends about such heavy-handed policies, saying, "It seems they won't leave us in peace," the group Free Tibet reported, citing local sources.
According to the Tibetan lobby group Free Tibet, the monk, Tamchoe Sangpo, was a teacher in the Bongthak Ewam Tare Shedrup Dhargey Ling Monastery in Themchen County in Qinghai Province, and a member of the monastery's management committee.
A day after the self-immolation of a Tibetan monk and reports of large protests in response, the advocacy group Free Tibet posted new video and photographs offering a rare glimpse of monks inside the highly restricted and restive part of western China.
