China on Monday warned government officials in Tibet that failing to maintain stability could result in job loss or criminal prosecution, the latest sign of heightened ethnic tensions in the remote Himalayan region.

The warning comes four years after deadly riots erupted in Tibet's capital, Lhasa, and as China enters a politically sensitive period with the top leaders of the ruling Communist Party changing by the end of the year.

There has also been a recent wave of unrest in ethnic Tibetan areas of Sichuan, a province adjoining Tibet, with more than a dozen monks and nuns setting themselves of fire over the last year and clashes erupting between Tibetans and security forces in recent weeks.

Monday's announcement on the official website of the Tibetan regional government said two cases of dereliction of duty had recently been reported and that such cases were to be handled harshly. It said authorities who mishandle emergency situations could lose their jobs or face criminal charges.

The announcement said "those responsible for problems in stability maintenance because they neglect their posts, act irresponsibly, abuse power or fail to carry out their duties ... will all be removed from their positions on the spot no matter who they are or what level they are at."

It said such cases could also be handed over to judicial authorities for criminal prosecution. It gave no details about the two alleged cases of dereliction of duty.

China says Tibet has been under its rule for centuries, but many Tibetans say the region was functionally independent for most of that time.

Over the weekend, an overseas rights group reported that three Tibetans in Sichuan's Seda county set themselves on fire Friday. If confirmed, the incidents would bring to at least 19 the number of monks, nuns and lay Tibetans believed to have set themselves on fire over the past year. Most have chanted for Tibetan freedom and the return of their spiritual leader, the Dalai Lama, who fled to India amid an abortive uprising against Chinese rule in 1959.

Chinese media have denied the latest claims that three Tibetans set themselves on fire. Western reporters trying to visit that part of Sichuan in the last several weeks have been turned away by security forces.

The unrest is the worst since 2008, when deadly rioting in Lhasa spread to Tibetan areas in adjoining provinces. China responded by flooding the area with troops and closing Tibetan regions entirely to foreigners for about a year. Special permission is still required for non-Chinese visitors to Tibet, and the Himalayan region remains closed off entirely for the weeks surrounding the March 14 anniversary of the riots that left 22 people dead.