Doctors say anti-Kremlin activist Verzilov is no longer in life-threatening danger after a likely poisoning.

It is “highly plausible” a member of Russian protest group Pussy Riot currently hospitalised in Berlin was poisoned, German doctors have said.

Kai-Uwe Eckardt of Berlin’s Charite hospital told reporters on Tuesday that Pyotr Verzilov was in intensive care since arriving at the hospital but that his condition was no longer life-threatening.

A prominent anti-Kremlin activist, Verzilov, 30, was flown to Germany on Saturday after falling sick with a mysterious illness last week, hours after an interview with Al Jazeera.

Eckardt told reporters the activist’s symptoms and information received from relatives and the Moscow hospital where he was initially treated indicated that a poisoning took place.

The Berlin hospital’s doctors had found “no evidence whatsoever that there would be another explanation for his condition,” Eckardt added, though they did not know what substance had caused the illness.

The symptoms indicated Verzilov is suffering from anticholinergic syndrome which can result from the disruption of the nervous system regulating the inner organs.

Hospital Chairman Karl Max Einhaeupl said there was nothing to indicate Verzilov had voluntarily taken a drug that caused the reaction.

“Such substances are extremely rare in drug circles,” he said.

“For someone to take this drug in such quantities, the person must have suicidal tendencies, and we have absolutely no indication of such intentions,” he added.

Verzilov was among the Pussy Riot members who served 15-day jail sentences for disrupting July’s World Cup final in Moscow.