Two monks set fire to themselves in a Tibetan town in western China on Monday, months after the brother of one of the men died in a self-immolation, according to the Free Tibet campaign.

The campaign group said Lobsang Kalsang and Lobsang Konchok, both aged 18 or 19 and from Kirti monastery in Aba county, Sichuan, had called for religious freedom and shouted "Long live the Dalai Lama" before burning themselves.

State news agency Xinhua said two monks had been rescued by police and had suffered slight burns and were in a stable condition, adding: "The suicide attempt is under further investigation."

In all, five monks have set fire to themselves in Sichuan within the last two and a half years.

Prior to that, the only known case of a self-immolation protest by a Tibetan was by a layman living in exile in 1998.

"It does suggest that this situation is getting out of control and that the efforts of the authorities in Sichuan to use the most aggressive techniques against one monastery – for reasons that have never been clear – are just making things worse," said Professor Robert Barnett, an expert on Tibet at Columbia University in New York.

"There have been suicides by Tibetan monks before, but they have never been public events … [they were] private statements of desperation."

Kirti is one of the largest Tibetan monasteries and Aba county saw fierce clashes in March 2008, when riots in Lhasa sparked wider unrest.

Tibetan exiles claimed security forces shot dead at least 10 people, while Chinese state media said that officers shot and wounded four people in self-defence.

The following year, one of Kirti's lamas set fire to himself, but is thought to have survived.

Tensions flared again when Lobsang Kalsang's 21-year-old brother Rigzin Phuntsog, also from Kirti, died after self-immolating in March.

Their uncle and another of their brothers were among six lamas recently sentenced for "intentional homicide" and other crimes in connection with his death.

Phuntsog's uncle, Drongdru, was jailed for 11 years for "intentional homicide", with the court finding that he had hidden his injured nephew, preventing medical treatment.

Exile groups said that monks rescued Phuntsog and took him back to the monastery because police were beating him rather than putting out the flames. A Xinhua spokesman denied he had been beaten.

Chinese officials also denied that Kirti was under lockdown by armed police following the incident.

Last month, 29-year-old Tsewang Norbu burned himself to death. He was a lama at Tawu monastery in Sichuan, about 150 miles from Kirti.

"Clearly the community in Ngaba [the Tibetan name for Aba] is feeling it is under immense pressure … My worry is that this is becoming a trend," said Stephanie Brigden of Free Tibet.

"It is not just the arrests [of Phuntsog's brother and uncle] but also house searches, monitoring and tracking of the family and anyone closely associated with it."

No one could be reached for comment at the Aba county government offices.

An employee at the public security bureau could be overheard telling a colleague: "This person is asking what happened in [inaudible] Square."

The colleague then took over the call, saying: "We do not have this information at hand."