Chinese security forces have shot and killed a young Tibetan man in Sichuan province, Tibetan campaign groups say.
The death in Aba prefecture would be at least the third such killing this week.
Police and troops opened fire when a crowd gathered to protect another man being sought for distributing leaflets in Aba, the Free Tibet group said.
There has been no official comment from Chinese authorities. Officials have confirmed that two Tibetans were killed in earlier protests in Sichuan.
The BBC's Damian Grammaticas says tensions have been rising in Sichuan, in south-west China, since a young monk died after setting himself on fire in Aba last March.
His actions have led to a wave of at least 15 more self-immolations by Tibetan monks and nuns.
This new incident happened on Thursday, Tibetan rights groups say, when a young man distributed posters in Warma saying the immolations would not stop unless Tibet was free and the exiled Tibetan spiritual leader the Dalai Lama was allowed to return.
Chinese police, it is claimed, moved in to arrest the young man and then fired when a crowd of Tibetans tried to prevent them from taking him away.
Campaign groups identified the dead man as a 20-year-old student called Urgen who was in the crowd.
Tibetan areas of Sichuan are extremely tense. Earlier this week Chinese police fired on demonstrations in the towns of Luhuo and Seda.
China's government said a mob had tried to storm a police station in one incident and confirmed two deaths.
Overseas rights groups said the marches were peaceful protests over mass arrests by security forces, claiming at least four Tibetans were killed and more than 30 injured.
The groups say the immolations and protests are a sign of rising frustration among Tibetans because of growing religious repression and harsh security measures adopted by China.
Tibetan areas of Sichuan are now said to be under a security lockdown with roadblocks, checks on all travellers, and internet and phone services cut, our correspondent says.