German doctors have announced that tests done on Russian opposition leader Alexei Navalny indicate he was poisoned.
The staunch critic of Vladimir Putin is currently in an artificial coma at Berlin’s Charité Hospital.
Doctors there have said that clinical results confirmed by independent labs indicate poisoning.
It is not clear exactly what substance was used against him, but it is believed to be a nerve inhibitor.
Navalny’s condition has been described as serious, but he is not thought to be in acute danger.
A statement from the hospital read: “The clinical findings indicate intoxication by a substance from the cholinesterase inhibitor group.
“The specific substance has not been identified so far and a further wide-ranging analysis has been initiated.
“The effect of the toxin, i.e. the cholinesterase inhibition in the organism, has been proven several times and in independent laboratories.”
Navalny was transferred from a Siberian hospital to Germany early on Saturday morning on a special medical plane.
His supporters, who believe a cup of tea he drank was poisoned by the Kremlin, have suggested that his transfer was delayed to ensure there would be no trace of poison left in his system by the time he arrived.
Russian doctors insisted they had found no poison and speculated that his Navalny’s ill health may have been caused by low blood sugar.
Early on Saturday morning, Mr Navalny’s spokeswoman Kira Yarmysh tweeted: “The plane with Alexei has taken off for Berlin. A huge thank you to everyone for your support.
“The struggle for Alexei’s life and health is just beginning and there will be much more to go through, but at least now the first step has been taken.”
Navalny, a 44-year-old politician and corruption investigator who is one of the Russian President’s fiercest critics, was admitted to an intensive care unit in Omsk on Thursday.
He had collapsed on a plane, with footage showing him howling in agony, on the same day after drinking tea that his allies believe was laced with poison.
Navalny has been a thorn in the Kremlin’s side for more than a decade, exposing what he says is high-level graft and mobilising crowds of young protesters.
He has been repeatedly detained for organising public meetings and rallies and sued over his investigations into corruption.
He was barred from running in a presidential election in 2018.