Tsewang Kyab set himself on fire Friday evening on the main street of Amuquhu town in Xiahe county, London-based Free Tibet said.
Earlier Friday, a 24-year-old Tibetan farmer, Lhamo Tseten, died from self-immolation near a military base and a government office in Amuquhu, the group said. China's official Xinhua News Agency reported the self-immolation of a Tibetan man by the same name, though details were slightly different. Xinhua said that Lhamo Tseten was a 23-year-old villager and that he set himself on fire near a hospital.
Calls to local governments in both Xiahe and the higher administration Gannan prefecture rang unanswered Saturday.
In the past week in Xiahe, which is in Gansu province, a herdsman, a farmer and a man in his late 20s also died after setting themselves on fire.
Dozens of ethnic Tibetans have set themselves on fire in heavily Tibetan regions since March 2011 to protest what activists say is Beijing's heavy-handed rule in the region. Many have called for the return of the Dalai Lama, their exiled spiritual leader.
Xiahe is home to Labrang Monastery, which is one of the most important outside of Tibet and was the site of numerous protests by monks following deadly ethnic violence in Tibet in 2008 that was the most sustained Tibetan uprising against Chinese rule in decades.
Police in the region are offering tipsters a reward of $7,700 for information about planned self-immolations in a bid to stem the tide of fiery protests.
The protests are coming at a sensitive time, with China's Community Party planning a once-in-a-decade power transfer in less than two weeks in Beijing.