MOSCOW (AFP) - Russian performance artist Pyotr Pavlensky, who is on trial for setting fire to the security service headquarters in a protest, on Tuesday accused guards of beating him and cracking his rib.

“As I write these lines, my knee has been injured, I have a cracked rib and internal bruising.... Every breath gives me pain,” Pavlensky said in a handwritten letter published on Facebook by his partner Oksana Shalygina, which blamed the assault on “the convoy guards of the Moscow City Court.”

Pavlensky faces up to three years in prison for dousing the door of the FSB building, the successor to the KGB, with gasoline and setting it on fire in November 2015 in a performance he called “Threat”.

The first full hearing in Pavlensky's trial on charges of damaging a cultural heritage site, will be held on Wednesday at Moscow’s Meshchansky district court.

Pavlensky's lawyer Dmitry Dinze confirmed the artist’s injuries to AFP, saying the beating occurred on Monday when his client was being taken back to prison after a court hearing.

Dinze said that Pavlensky was attacked by a single guard and that the lawyers would try to identify him. Shalygina wrote the badge number of the guard allegedly responsible on Facebook.

A spokeswoman for Moscow City Court, Ulyana Solopova, told Russian news agencies the court was not responsible for the transfer of defendants back to detention centers and that this is carried out by police.

Pavlensky is currently being held in Moscow's Medvedkovo prison. During the investigation, he spent a month in a psychiatric hospital undergoing tests of his sanity, which found he was mentally capable.

The 32-year-old activist is known for such brazen acts as nailing his scrotum to the cobblestones of Red Square in November 2013 and for cutting off his earlobe in another protest a year later.

- 'Creative dissent' prize -

He is also currently on trial for a Saint Petersburg performance called “Freedom” in 2014 in which he set fire to tires in a nod to the pro-Western rallies in Kiev.

During a hearing last month in that case, Pavlensky brought sex workers into court to testify against him in an apparent bid to expose the court system as unethical and corrupt.

The verdict in that vandalism case is expected on Thursday. Prosecutors have asked for Pavlensky to be sentenced to a punishment not involving jail, which will be immediately lifted because of the statute of limitations rules.

At the same time, Pavlensky this month is one of three recipients of the annual Vaclav Havel international prize “for creative dissent,” an annual award established by the US-based Human Rights Foundation (HRF). Iranian cartoonist Atena Farghadani and Uzbek photojournalist Umida Akhmedova are the two other laureates.