China has warned officials in Tibet that they must maintain stability ahead of the fourth anniversary of deadly unrest in Tibet's capital, Lhasa.
China has increased security in Tibet and adjoining provinces following a series of self-immolations and sporadic protests against Chinese rule.
On Monday, the India-based administration of Tibetan exiles cited "unconfirmed reports" that three Tibetans set themselves on fire Friday in Serthar, a Tibetan area of China's Sichuan province. If confirmed, it would bring to at least 19 the number of monks, nuns and lay Tibetans believed to have burned themselves over the past year.
Chinese media has denied the reports.
The unrest is the worst since 2008, when 22 people died in rioting in Lhasa and Tibetan areas in adjoining provinces.
In a statement from its seat in the northern Indian town of Dharamshala, the exiled Tibetan government said the spate of self-immolations "indicate to us that the Chinese policies in Tibet have reached new levels of repression.''
China, in turn, blames exiled Tibetans for stoking the protests, especially Tibet's spiritual leader the Dalai Lama, who fled to India in 1959 after a failed uprising.