Russian news reports say a member of Russian punk protest group Pussy Riot has been hospitalised in grave condition for what could be a possible poisoning.

Relatives told the Meduza online news portal that Pyotr Verzilov had been undergoing emergency care since Tuesday.

They said he fell ill after a court hearing for Veronika Nikulshina, a fellow member of the anarchist, art protest group.

News report quoted her saying his symptoms included losing his eyesight and ability to hear.

Ms Nikulshina said Mr Verzilov was being treated in the toxicology unit of a Moscow hospital, indicating a suspected poisoning.

Mr Verzilov, Ms Nikulshina and two other activists served 15-day jail sentences for disrupting July's World Cup final.