BEIJING — The top Communist Party official in the Lhasa, the Tibetan capital, has urged security personnel to step up surveillance of monasteries and along pivotal roads through the region during what he warned would be a period of heightened social turbulence.
 
“Strive to realize the goal of ‘no big incidents, no medium incidents and not even a small incident,’ ” the official, Qi Zhala, said in comments published on Tuesday in the state-owned Tibet Daily.

The comments came at time of increasing tension in ethnically Tibetan parts of China, especially in the southwestern province of Sichuan.

 Last week at least three people were shot and killed by Chinese forces during protests in the remote, mountainous portions of the province bordering Tibet, according to Tibetan exile groups outside China. Scores of others were reportedly wounded, although the reports could not be verified because the entire region is off-limits to foreign journalists.

The government-run news media have vacillated between censoring accounts of the episodes and blaming the Western media for exaggerating the violence. Many of the injured, government-run news outlets said, were actually police officers wounded after Tibetan protesters attacked police stations or opened fire.

The episodes, the most serious outburst of unrest since anti-Chinese rioting killed 18 people in Lhasa in 2008, follow a spate of self-immolations that have bedeviled the authorities. In recent months 11 people, most of them Buddhist monks and nuns, have died after setting themselves on fire.

Exile groups say the self-immolations, numbering at least 16 in the past year, are desperate acts of protest against Beijing’s heavy-handed policies; the Chinese government says they are orchestrated by the Dalai Lama, the exiled Tibetan leader, in an effort to gain international sympathy for his cause.

In his comments, Mr. Qi, the powerful Communist Party chief in Lhasa, urged the authorities who oversee China’s heavily Tibetan provinces to coordinate their efforts and to focus on monasteries and “key suspects” who are prone to fomenting trouble.

“We must strike hard at all the separatist, destructive and criminal activities of the Dalai clique,” he said, adding that religious and government leaders would be dismissed if they failed to maintain stability.

Mia Li contributed research.