By Michael Martina
BEIJING (Reuters) - Two Tibetans in China's southwestern Sichuan province were killed when security forces fired on demonstrators, a Tibetan advocacy group said, upping the death toll in several clashes over government controls to four since Monday.
The violence is likely to add to rising tensions in the rebellious Tibetan highlands of Sichuan that border Tibet, where security forces have struggled to maintain control over heavily Buddhist communities.
At least two people were shot dead and many were wounded during protests in Seda County on Tuesday, the London-based Free Tibet group said late the same day.
"Locals describe the town as being under curfew: they have been told not to leave their homes and they are now afraid that if they do they will be shot," the group said in a statement.
Calls to the county government and public security bureau, about 680 km (423 miles) west of Sichuan's capital of Chengdu, were not answered.
But on Wednesday, the official Xinhua News Agency confirmed the clashes in Seda, saying police were forced to open fire killing one "rioter" when protesters attacked a police station with gasoline bottles, knives and stones.
"Police were forced to use force after efforts involving persuasion and non-lethal weapon defense failed to disperse the mob," Xinhua said, adding that 14 police officers were injured and 13 people were arrested.
The news agency earlier confirmed a separate clash on Monday in Luhuo township, called Drango or Draggo by Tibetans, in the western highlands of Sichuan near Tibet. It said one protester was killed and five police officers were hurt.
Free Tibet in a separate statement late on Tuesday said it had confirmed that at least two Tibetans had been killed in Monday's incident in Luhuo and that it had the names of 36 people wounded in the clash.
The group, which campaigns for Tibetan self-determination, also said that troops fired teargas in a third location in Sichuan -- Meruma township, Aba County, called Ngaba County by Tibetans -- after people protested.
Security forces have been on edge after 16 incidents of Tibetans setting themselves on fire over the past year in response to resentment of Beijing's controls on religion.
Most of the incidents occurred in Sichuan. Some of the protesters have called for the return of the Dalai Lama, the exiled Buddhist leader revered by many Tibetans.
Other advocacy groups and a resident in a village near Luhuo reached by Reuters had slightly varying accounts of the incidents, which are difficult to verify because the government restricts travel to Tibet and parts of Sichuan.
The Tibetan government in exile in India said on its website five people had been shot dead in the two incidents.
ON THE DIPLOMATIC BACKBURNER
The clashes come at an awkward time for China as Vice President Xi Jinping -- expected to replace President Hu Jintao in a leadership handover late this year -- prepares for a visit to Washington in February.
U.S. Special Coordinator for Tibetan Issues Maria Otero said in a statement the United States was "gravely concerned" about the reports of violence.
"The U.S. government repeatedly has urged the Chinese government to address the counterproductive policies in Tibetan areas that have created tensions and that threaten the distinct religious, cultural and linguistic identity of the Tibetan people," Otero said.
Analysts, however, say the government's policies leave little hope of easing tension, and China's economic influence has put other countries' efforts to broach human rights -- including those of the United States -- on the backburner.
"What dominates the U.S.-China relationship has more to do with trade and economics than human rights and Tibet," Nicholas Bequelin, a researcher with Human Rights Watch, said.
"We have to consider that even though these policies are failing to win over Tibetans to the Chinese state, they are very effective in cementing China's control," Bequelin said. "It seems the leadership has made the calculation that it can rule without the consent of Tibetans."
China has ruled what it calls the Tibet Autonomous Region since Communist troops marched in in 1950. It rejects criticism that it is eroding Tibetan culture and faith, saying its rule has ended serfdom and brought development to a backward region.
The Dalai Lama fled Tibet in 1959 after a failed uprising against Chinese rule.
China's Foreign Ministry has branded the self-immolators "terrorists" and has said the Dalai Lama, whom it condemns a supporter of violent separatism, should take the blame.
(Additional reporting by Chris Buckley and Max Duncan in Beijing, Farah Master in Hong Kong, and Madhukar Abhishek in Dharamsala, India; Editing by Nick Macfie)