Tibetan Government in Exile Prime Minister Lobsang Sangay told the Financial Times newspaper that images sent to his government by people in Tibet leads him to believe "the military buildup is increasing rapidly."
"We've seen pictures of hundreds of convoys filled with paramilitary forces with automatic machine guns moving toward various parts of Tibetan areas," he said.
"We're really worried that with such a military security buildup and so many guns in the hands of Chinese police and military personnel, we fear the Chinese government is preparing for something very drastic and unforeseen and tragic."
Sangay's fears come as more reports of self-immolations come out of Tibet.
One Tibetan has died and two others are believed to have survived the latest acts of self-immolation in Tibet, the Free Tibet Web site said last week.
The three set fire to themselves in a village around 90 miles from Serthar in Sichuan province where Chinese forces recently fired on Tibetans, killing at least two, Free Tibet said.
Much of the protest has centered in Sichuan province, in particular near the Kirti Buddhist monastery. The area around the monastery Kirti Gompa, founded in 1472 on the edge of Ngaba or Aba City, has been tense since Rigzin Phuntsog, a monk, set himself on fire and died last March.
Many Tibetans in Sichuan, a province directly east of Tibet, are angry about what they see as a ploy by Beijing to move ethnic Han Chinese into the majority Tibetan areas of Sichuan. Tibetans say it is a direct policy by Beijing to make Tibetans a minority in their own land.
Residents of the Xinjiang Uighur Autonomous Region have made similar allegations.
Sangay told the Financial Times that he and the Dalai Lama, the 76-year-old Tibetan Buddhist spiritual leader, are on record as calling for Tibetans, many of them monks and nuns, to refrain from extreme actions including self-immolation.
But "their sentiment is so strong they are choosing to die rather than live," Sangay said. "This shows that the Chinese government's repressive policies in Tibet have clearly failed."
In an exclusive interview with the BBC in November, the Dalai Lama denied accusations by Beijing that he is actively encouraging Tibetans to set themselves on fire in public places.
He questioned the usefulness of the acts as a protest tool against the Chinese authorities and their more than 50 years of rule in Tibet.
"There is courage -- very strong courage" by the people who set themselves on fire. "But how much effect? Courage alone is no substitute. You must utilize your wisdom."
Beijing and the Dalai Lama have been waging a war of words since he fled Tibet soon after the Chinese army marched into Tibet in the late 1950s. The Dalai Lama and many of his followers have been living in exile in northern India.
Beijing has never recognized the Tibetan Government in Exile and often blames it and the Dalai Lama for fomenting separatism in Tibet.
In July, Chinese Vice President Xi Jinping, the man believed to be China's leader-in-waiting, said he will "smash" any plan to undermine Tibet's place within China.
But while asserting the need for social stability, Beijing also stresses its increased aid to help the economy and improve the daily life of millions of rural Tibetans.
Last week, the official government news agency Xinhua reported the Tibet Autonomous Region government had "earmarked more than $1.3 billion this year to improve the living conditions of farmers and herdsmen in the region," which accounts for around 80 percent of the Tibetan population.
The amount is two-thirds more than last year, the Xinhua report said. Money will be used for rural infrastructure construction and agricultural subsidies.
"Some of the money will also be used to encourage farmers to modernize and industrialize their work and to develop Tibetan-featured industries," Xinhua said.