The monk is reportedly being treated for his wounds after the protest in Changdu, known as Chamdo in Tibetan. If confirmed, the incident would be the first self-immolation in the Tibetan Autonomous Region. Activists say 11 monks and former monks have set themselves on fire this year, but the incidents have all taken place in Tibetan areas of Sichuan Province. Access to the Tibetan Autonomous Region is tightly restricted, and information is difficult to corroborate. Radio Free Asia reported that the monk, a 46-year-old named as Tenzin Phuntsog, had scattered leaflets and shouted slogans before setting fire to himself on Thursday afternoon. The US-based broadcaster quoted an anonymous source living in India, and another source calling from Tibet as confirming the incident. "[The former monk] was very frustrated by the recent imposition of restrictions on Karma monastery and by the detention of many monks. There was even talk by Chinese officials of closing the monastery," the source in Tibet was quoted as saying. The US-based International Campaign for Tibet said accounts of the incident had also been uploaded to Facebook and micro-blogs in the Tibetan language.

Moscow city prosecutors opened an investigation into Golos after it listed thousands of complaints about election campaigning on its website.

Golos is accused of breaking pre-election reporting restrictions.

The US-based campaign group Human Rights Watch (HRW) said Golos was the victim of a smear campaign.

"They are trying to shut it up because Golos is the only large-scale, serious organisation that is exposing election violations," Tanya Lokshina of HRW's Moscow branch told Reuters news agency.

Russia elects a new parliament on Sunday and will hold a presidential poll on 4 March, when Vladimir Putin will stand for re-election after two previous terms in the post.

The outgoing parliament, or State Duma, is dominated by his party, United Russia, with seats also held by the Communist Party, the nationalist Liberal Democrats and the social-democratic Fair Russia.

Under Russian electoral law, media broadcasting to Russian territory are not allowed to report the results of opinion polls in the five days leading to the election.

'Negative image'

Golos (which means "voice" in English) is a widely respected election watchdog funded by the EU and US. It provides training for observers and runs a website compiling complaints of voting violations.

As of Friday afternoon, it had recorded nearly 5,000 complaints related to Sunday's election, many involving United Russia.

According to the court documents, Golos is accused of having reported "election-related opinion polls and research" between Tuesday and Wednesday.

The prosecutors specify that such data includes "results of analysis of reports of violations".

Golos is accused of "effectively creating among voters a negative image of one of the parties".

Vladimir Churov, head of Russia's central election commission, was quoted by Russian media as saying this alleged bias referred to United Russia.

Russian MPs have also questioned why Golos, a foreign-funded organisation, is allowed to monitor Russian elections.

Grigory Melkonyants, deputy head of Golos, told Reuters that his organisation was being subjected to a "premeditated campaign, which started with attacks in the press, but is now making use of law enforcement agencies".

Referring to a court summons for Thursday, he added: "We are certain this is only the first summons and there will be other investigations, especially targeted at hampering us from observing [the election] on 4 December."

In a televised address on Friday, President Dmitry Medvedev insisted Russia's political parties enjoyed "free and equal competition" ahead of the election.

Without naming United Russia, he urged voters to choose "responsible politicians, who can help improve our people's living standards in practice, and who will be guided in their actions by the interests of voters and national interests".