Dharamsala (AsiaNews / Agencies) - A young boy just out of his teens has become the third Tibetan to set himself on fire this week to protest against Beijing's rule in Tibet, according to sources from an activist group in exile, while the Beijing government has strengthened security measures in view of the anniversary of the uprising of 2008. Last year alone more than 20 Tibetans - the vast majority of monks - self-immolated in their battle to defend human rights, greater autonomy and religious freedom. The latest official victims emerged yesterday: a mother, a widow with four children and a girl between 16 and 19 in Gansu.

In a statement released by Free Tibet and International Campaign for Tibet, a boy of 18 - known by the name of Dorjee - yesterday afternoon chanted anti-China slogans outside a government office of the Prefecture of Aba, Sichuan Province . He is reported to have died at the scene and only later security officers intervened, to remove the corpse.

The police in Aba, which has a large Tibetan community and has become an icon of the protest, declined to comment on the story or provide confirmation.

Human rights activists say the escalation in self-immolations - a recent phenomenon in the Tibetan anti-Chinese protests - is a sign of growing desperation among the representatives of ethnic minority, who tried to contest (unsuccessfully) the record in Beijing Himalayan region.

Since March 2008, after the Lhasa uprising bloodily repressed by the police, the Chinese government has tightened security measures in the area and control the activities of monasteries and monks, so that the protest does not expand to other areas of Country. China denies that it is implementing repression, and adds that, now, Tibetans live a better life thanks to investments and infrastructure made by Beijing.

However, in recent months, tension has grown, particularly so that the western part of Sichuan province, which borders the Tibetan region with an increasing number of riots and self immolations.