Gravely ill Kremlin critic Alexei Navalny was evacuated to Germany for medical treatment on Saturday, flown out of the Siberian city of Omsk in an ambulance aircraft and taken to a hospital in Berlin.

There was no word yet from the Charite hospital on his condition but the founder of the activist group that arranged the flight called Navalny’s health condition “very worrying”.

A long-time opponent of President Vladimir Putin and campaigner against corruption, Navalny collapsed on a plane on Thursday after drinking tea that his allies believe was laced with poison.

Medical staff at the hospital in Omsk said on Friday evening, after clearing Navalny to be flown out, that he was in an induced coma and his life was not in immediate danger.

The air ambulance, arranged by the Cinema for Peace Foundation, flew to Berlin’s Tegel airport early on Saturday and Navalny, 44, was rushed to the Charite hospital complex.