Tibetans who set themselves on fire in protest at Chinese rule face "extreme physical and psychological suffering" if they survive, a rights group said, alleging amputations, repression and forced disappearances.

The report by the International Campaign for Tibet (ICT) detailed the cases of 20 Tibetans since 2009 who survived self-immolation in China.

It also documented three such incidents involving Tibetans in exile.

More than 130 Tibetans have set themselves alight since 2009, ICT said, with the vast majority dying as a result.

Some survivors have been returned home, the group said, but "in most other cases their families are still unaware of whether they are dead or alive, even years after their self-immolation".

Survivors "face extreme physical and psychological suffering due to repressive measures against them by the Chinese authorities", it said.

ICT President Matteo Mecacci said in a statement that survivors "have generally been held by the authorities in conditions of extreme secrecy and isolation".

"In some cases, families have only become aware of their relative's situation when they have been shown in Chinese state media propaganda blaming the Dalai Lama for their actions," he added.

The report, released late Thursday, detailed the cases of four Tibetans who had limbs amputated after they failed to burn themselves to death.

One of them, a 17-year-old monk named Sungdue Kyab, was returned home nearly two years later, having lost both his legs.

"Some Tibetans fear that such amputations followed a period of time in custody in which full medical treatment is not given," the report said, adding that amputations also "may be a form of punishment to the self-immolator".

Access to Tibet is tightly restricted by Beijing, with foreign journalists effectively barred from visiting, making it difficult to independently verify information.

One monk named Tapey who attempted to burn himself to death in 2009 later featured in a state-run media video that blamed the Dalai Lama for instigating self-immolations, ICT said.

Self-immolations among Tibetans peaked in the run-up to the ruling Communist Party's pivotal five-yearly congress in November 2012, but have become less common in recent months.

Last week, a Tibetan woman burned herself to death in the first such incident this year, according to rights groups.

Many Tibetans in China accuse the government of religious repression and eroding their culture, as the country's majority Han ethnic group increasingly moves into historically Tibetan areas.

Beijing says it has brought development to Tibet and condemns the self-immolations, blaming them on the Dalai Lama and saying the exiled spiritual leader uses them to further a separatist agenda.

The Dalai Lama, a Nobel Peace laureate, has described the burnings as acts of desperation that he is powerless to stop.