Alexei Navalny’s press secretary has urged Russian authorities not to interfere as supporters of the stricken opposition leader prepared to fly him out of the country to be treated for a suspected poisoning.

A plane left Nuremberg with a medical team in the early hours of Friday and, according to German media, would head to Omsk before returning to Berlin with Navalny, where the Charité hospital was ready to treat him.

Jaka Bizilj, founder of the German NGO Cinema for Peace Foundation, told newspaper Bild: “The plane is in the air, we have all the necessary paper and hope that Alexei is ready for transport tomorrow morning so that we can fly to Berlin.”

In a video statement released on Thursday night, she said: “We ask the management of the hospital where Alexei is lying now not to obstruct us in obtaining all the documents necessary for his transfer

Navalny was flying from Tomsk in Siberia to Moscow on Thursday when he suddenly fell ill and lost consciousness, prompting the captain to make an emergency landing in Omsk. Mobile video shot on the plane showed medical personnel rushing onboard as Navalny screamed.

Navalny, 44, was in a coma and on a ventilator in intensive care in Omsk, said Yarmysh on Thursday. She advised against trusting any other sources of information on Navalny’s health.

Hospital officials in Omsk have given contradictory information about his condition and have not allowed his family or supporters in to see him. Anatoly Kalinichenko, the deputy chief doctor of the hospital, confirmed that Navalny was unconscious and on a ventilator, but called his condition “stable”. Doctors “are currently engaged in the process of saving his life”, he said on Thursday afternoon.