Vladimir Putin’s nemesis, corruption fighter Aleksey Navalny, is fighting for his life in a Siberian hospital after allegedly being poisoned at an airport while travelling to Moscow.

Navalny’s closest aide, Kira Yarmysh, said Navalny was poisoned after drinking a cup of tea at Tomsk airport early Thursday morning. He then boarded a flight to the Russian capital but fell violently ill en route. Taken from the aircraft on a stretcher after it was diverted to the city of Omsk, the opposition leader is in intensive care, relying on a respirator to breathe.

A Russian DJ who was on the same flight recorded a video that showed medical help arriving after the plane landed in Omsk. Navalny’s screams could be heard in the background.