Pyotr Verzilov
© ReutersPyotr Verzilov arrives on a special medical transport plane at Schoenefeld airport in Berlin, Germany September 15, 2018
Doctors in Berlin who are treating controversial underground artist and Pussy Riot activist Pyotr Verzilov, say that he was probably poisoned by an unknown substance.

"The impression and the findings that we now have, as well as those provided by colleagues from Moscow, suggest that it was highly plausible that it was a case of poisoning," Kai-Uwe Eckardt, a leading doctor at Berlin's Charité Hospital said, as cited by AFP.

Verzilov's health "was improving from day to day" and he is "no longer in life-threatening danger,"according to the hospital's chairman Karl Max Einhaeupl. He ruled out the possibility that it was a case of self-inflicted substance abuse. "Such substances are extremely rare in drug circles and we have no indication that it was a drug problem," he said.

The 30-year-old artist who has both Canadian and Russian citizenship was taken to a Moscow hospital earlier in September. According to his family, Verzilov felt ill and complained his eyesight was failing. Later he was transported to Germany by the Cinema for Peace Foundation which has long supported members of Pussy Riot. The artist's family insists that he was poisoned.

Verzilov became notoriously popular for his involvement with the art group Voyna ("war"). The organization was behind dozens of protests, including public displays of sex in Moscow's Timiryazev State Museum of Biology before the election of Russian President Dmitry Medvedev. The group once threw live cats at a McDonald's restaurant in the Russian capital during the International Workers' Day.

He also made music videos for the punk band Pussy Riot. The feminist group was tried for hooliganism because they shot footage inside a church and used blasphemous lyrics in 2012. The whole trial was presented by Western mainstream media as persecution of artists for their anti-government message. Verzilov, who was married to one of the group's members, Nadezhda Tolokonnikova, at that time, wasn't a defendant during the case.

The artist's most recent 'performance' took place in July this year during the final game of the FIFA 2018 World Cup, when he and several women - all members of Pussy Riot - ran across the pitch while dressed in fake police uniforms. The performers were sentenced to 15 days of administrative detention and given small fines. The activists explained that the incident was aimed at highlighting abuses by Russian police and the plight of alleged "political prisoners."