Garry Kasparov, the Russian opposition leader and former international chess champion, has been cleared of charges of assaulting a police officer in a Moscow court, in a decision he called "historic".

Kasparov was arrested on August 17 outside of the courthouse where members of the punk protest group Pussy
Riot were being sentenced.

He was accused of biting an officer on the hand following his detention.

"I think it's a very important day, a historical day, because for the first time in our courts, the evidence of a policeman was not accepted just because they wear a uniform," Kasparov told journalists after the decision was announced on Friday.

Kasparov had been among about 100 protesters who were detained outside of the Pussy Riot verdict reading.

He had gone to support the women who received two-year sentences for "hooliganism motivated by religious hatred" for storming the altar of Moscow's main cathedral in February and signing a song calling on the Virgin Mary to get rid of Russian President Vladimir Putin.

As he gave an interview to journalists outside of the court, he was grabbed by police officers and carried to a waiting police van, in an arrest caught by a Reuters news agency cameraman and viewed by thousands on the internet.

Kasparov claimed he was illegally detained for violating rules pertaining to protest rallies and was beaten and then falsely accused of biting an officer on the hand following his arrest.

On Friday, a judge agreed with the Putin critic's assessment, and said video of the incident contradicted police statements.

"So the court acted unbiased. It accepted all of the video evidence, it questioned journalists, witnesses who were nearby, and stated that the policemen's evidence was extremely controversial," Kasparov said.

"It was factually false testimony. And the court made its decision based on that."

He added that he would press charges against police for wrongful arrest and slander.