BEIJING (AFP) - A Tibetan mother-of-two burned herself to death to highlight repression in the Chinese Himalayan region, overseas media and rights groups said, the second such fiery protest in eight days.

Sangye Tso died after setting herself on fire in Zhouni, a Tibetan-majority area of the north-western Chinese province of Gansu, sources told Radio Free Asia (RFA), which is backed by the US government.

The Washington-based International Campaign for Tibet (ICT) said the 36-year-old was "believed" to have killed herself in Wednesday's protest, which it said was staged outside a "government building".

RFA said her self-immolation took place outside a "Chinese police headquarters". It is the 141st such act in Tibet and elsewhere since 2009, most of them fatal, it said.

The woman is survived by her husband, son and daughter, both reports said.

However, an official in Zhouni, in Gannan prefecture, denied the immolation had taken place.

"No, it didn't happen at all," he told AFP.

The reports come after a father of four was last week said to have set himself on fire in the south-western Chinese province of Sichuan, which is also home to many Tibetans.

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

Beijing condemns the self-immolation protests and blames them on exiled Tibetan leader the Dalai Lama, saying he uses them to further a separatist agenda.

It also says it has brought development to Tibet and says it upholds minority and religious rights in a country with 56 recognised ethnic groups.

The Dalai Lama, a Nobel Peace laureate who has lived in India since 1959 after a failed uprising in Tibet, has described the burnings as acts of desperation that he is powerless to stop.