A Tibetan woman burned herself to death days before the anniversary of a failed uprising against Chinese rule, a rights group and media said, in the first such incident this year.

The woman in her 40s, whose name was given only as Norchuk, set herself alight Friday near Trotsuk township in Aba county in the southwestern province of Sichuan, the British-based Free Tibet campaign group and US-funded Radio Free Asia (RFA) both said.

It was the first self-immolation in Tibetan areas this year and came days before March 10, the anniversary of the failed uprising in 1959 that led Tibet's spiritual leader the Dalai Lama to flee into exile in India.

Norchuk is the 137th Tibetan known to have set themselves on fire since 2008, RFA said at the weekend, and was affiliated with a monastery in the area. Its Chinese-language report said she had one son and two daughters.

Her body was cremated by the local government, Free Tibet said late Sunday, "preventing her family and community from carrying out traditional funeral ceremonies".

But an official with the Communist Party's office in Aba county on Monday denied the reports.

"The reports are wrong," she told AFP, adding there had not been any self-immolations in the area in recent days.

Security in many Tibetan areas has been tightened recently, RFA said.

It cited locals as saying the move was aimed at intimidating Tibetans who wanted to celebrate religious observances during the Lunar New Year, and preventing protests on Tuesday's anniversary.

Pictures have emerged on social media of a heavy security presence at Kumbum monastery in Qinghai for the Monlam prayer festival last week, showing dense ranks of uniformed personnel in a courtyard.

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.

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

Beijing condemns the acts and blames them on the Dalai Lama, saying he 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.