The nun's case brings the total number of religious people, including monks and former monks, who have set themselves on fire this year in Sichuan to 9. Seven of them have done so in the past month, and they were all from Aba, according to Tibetan rights groups. Among the 9, at least five died.

'Information from Tibet suggests that there are more who are willing to give their lives. They are determined to draw global attention to the persistent and brutal violations Tibetans suffer under Chinese occupation,' said Stephanie Brigden, director of London-based Free Tibet.

'The acts of self-immolation are not taking place in isolation. China has already responded with force in one instance. We have grave concerns that greater force may be deployed if protests spread.'

Tenzin Wangmo set herself on fire at 1pm on Monday on a crossroad near her nunnery, known as Mame, about 3km from Aba.

She shouted slogans calling for the return of the Dalai Lama and religious freedom as she burned, Free Tibet said.

Her act came one day after Chinese security personnel reportedly shot two Tibetans at a protest outside a police station near Seda county, Ganzi prefecture, near Aba. One was shot in the leg and another in the torso, according to rights groups.

Because of the desperate acts, the Tibetan government-in-exile earlier called for a day-long prayer today in Dharamsala, India, that the Dalai Lama was set to attend.

Chinese Foreign Ministry spokesman Liu Weimin denied any improprieties in handling the cases.

'Some overseas media and some organisations have been playing up the issue,' Liu said. 'In fact, police rescued the self-immolated persons and rushed them to hospital. There has been no torture or anything like that.'

He said he had not heard of police allegedly opening fire on Tibetans in Sichuan over the weekend, and said it was merely 'some organisations spreading rumours'.

Meanwhile, Tibetan rights groups pointed to the growing religious repression in Aba, especially in the region's biggest monastery, the Kirti Monastery, as the root cause for turning to such forms of protest.

'The tight control began in March 2008 when more than 10 innocent Tibetans were killed by Chinese police in riots in Aba,' Tibetan poet Woeser said. 'But since a monk from Kirti self-immolated in 2009, the situation has only gotten worse.

'They have been asking for the government to relax controls, but no one listened. Since individual cases did not catch attention, they are probably hoping that it might if they do it in such concentration,' Woeser said.

Additional reporting by Teddy Ng