Beijing has appointed a career law enforcement official to head an ethnically Tibetan area of southwest China where a number of monks and nuns have self-immolated in recent months.

An official Communist Party website for Sichuan province's Aba prefecture -- scene of some of the worst protests against Chinese rule over the past year -- said Liu Zuoming was appointed on February 11.

At least 20 Tibetans have set fire to themselves in the past year to protest against what they call religious and cultural repression by Beijing, leading the government to impose virtual martial law in Tibetan-inhabited regions.

Many have been monks from Aba's Kirti monastery, which has been under virtual lockdown since a young monk named Phuntsog set light to himself and died in March 2011, sparking mass protests there.

Liu, 54, who previously worked as the government prosecutor in Sichuan, said he would make maintaining stability in Aba his priority, according to the government website.

"We must strictly prevent and severely strike at the activities of domestic and foreign hostile forces seeking to split, infiltrate and sabotage," he said.

"We must thoroughly smash any plot seeking to sabotage the stability of Aba and endanger the unity of the motherland."

China has routinely accused overseas groups and Tibet's exiled spiritual leader the Dalai Lama of advocating Tibetan independence, fomenting unrest and spurring monks toward self-immolation.

The Buddhist spiritual leader has denied such accusations, while calling for real autonomy for his Tibetan homeland.

Tibetans have long chafed under China's rule over the vast Tibetan plateau, accusing Beijing of curbing religious freedoms and eroding their culture and language, and these tensions have intensified over the past year.

But Beijing insists that Tibetans enjoy religious freedom and have benefited from improved living standards brought by China's economic expansion.