MOSCOW: Doctors in the Siberian city of Omsk refused to authorize the transfer of opposition politician Alexei Navalny to a German hospital, Navalny’s spokeswoman Kira Yarmysh said on Twitter.

Navalny remains in a coma in intensive care after a suspected poisoning his allies link to his political activity.

“The chief doctor said that Navalny is non-transportable. (His) condition is unstable. Family’s decision to transfer him is not enough,” Yarmysh said in a tweet.

The 44-year-old Navalny fell ill on a flight back to Moscow from the Siberian city of Tomsk on Thursday and was taken to a hospital after the plane made an emergency landing in Omsk. His team says an airplane with all the necessary equipment is ready to take Navalny to a German clinic.

Navalny’s ally Ivan Zhdanov said Friday that police found “a very dangerous substance” in Navalny’s system, but officials refuse to disclose which substance it is.