Image caption There are large communities of ethnic Tibetans in several parts of Sichuan province

Three Tibetans have set fire to themselves in south-west China, reports say, in the latest apparent protest against rule from Beijing.

US-based Radio Free Asia said they had called for the return of Tibetan spiritual leader the Dalai Lama during the protest in Sichuan province.

Exiled activists said one Tibetan died and the others had serious injuries.

If confirmed, the latest protest would mean 19 Tibetans had self-immolated in the past year and 13 of them had died.

Most of the protesters are Buddhist monks or nuns.

Western Sichuan is home to hundreds of thousands of Tibetans.

The BBC's Michael Bristow in Beijing says the authorities have launched a heavy security crackdown, sealing off much of the area.

Telephone lines have been cut and checkpoints have been set up along main roads, he says.

The Tibet Divide China says Tibet always part of its territory

Tibet had long periods of autonomy

China launched a military assault in 1950

Opposition to Chinese rule led to a bloody uprising in 1959

Dalai Lama fled to India

Radio Free Asia quoted exiled sources saying the latest immolations took place in a village in Seda county on Friday.

The UK-based Free Tibet group issued a statement with a similar account of the incident.

However, an unnamed official at the local government told the Associated Press news agency on Sunday that "no such thing happened".

A Tibetan was shot dead by security forces in Seda town on 25 January, some 145km (90 miles) from the latest incident.

International media are denied access to the area, making it difficult to verify conflict accounts.

Beijing has described the self-immolators as terrorists.

Officials have also blamed outside forces, particularly the Dalai Lama, for encouraging these act of defiance.

He denies that and blames the heavy-handed treatment of Tibetans for causing discontent.