The Russian opposition leader is fighting for his life after drinking tea that allies believe was laced with poison.

Putin critic Alexei Navalny is in a coma after a suspected poisoning.

Doctors have banned Alexei Navalny, the Putin critic who is in a coma after a suspected poisoning, from being transported abroad.

His spokeswoman said doctors had caved to Kremlin pressure - but a head doctor said the decision was made because he was not well enough.

A plane had apparently been due to transport him to Germany for treatment following the alleged poisoning.

The long-time critic of President Vladimir Putin, 44, is fighting for his life on a ventilator after drinking tea that allies believe was laced with poison.

He fell ill on a flight back to Moscow from Tomsk, a city in Siberia, and was taken to a hospital after the plane made an emergency landing in the Russian city of Omsk.

Mr Navalny's wife cited a police officer as saying a "very dangerous" poison had been detected in his body that posed a risk to everyone around him who should therefore wear protective suits, local media reported.

However on Friday, head doctor Alexander Murakhovsky declined to answer questions whether Mr Navalny was poisoned or not and is yet to confirm a diagnosis.

He said the Russian opposition leader's condition had improved a little, but that it was still unstable and that attempting to move him could pose a risk to life.

Kira Yarmysh, Mr Navalny's spokeswoman, said doctors claimed his condition was unstable and that the hospital refused to move him to another facility against his family's wishes.

She wrote on social media: "The ban on the transportation of Navalny is only needed to stall for time and wait until the poison in his body can no longer be traced.

Moreover, every hour of delay creates a critical threat to his life."

Russian opposition leader Alexey Navalny (@Navalny) has been reportedly poisoned, he is now in intensive care in serious condition. His spokeswoman suspects the toxin was hidden in his tea.

Read: https://t.co/D087CMVQWWpic.twitter.com/jUEYHnNJ6S

— Anonymous 🐈‍⬛ (@YourAnonCentral) August 20, 2020

Ms Yarmysh said a German air ambulance with a team specialised in treating coma patients was due to land in Omsk at around 6am, and that doctors had previously agreed to move him, but had changed their mind at the last minute.

"This decision, of course, was not made by them, but by the Kremlin," she said.

The Kremlin said on Thursday that medical authorities would promptly consider any request to move Mr Navalny to a European clinic and were being open about his condition.

Mr Navalny's allies want to take him out of the country to be treated, but Dr Murakhovsky said many legal questions would need to be resolved before that could happen.

He said top doctors had been flown in from Moscow to treat the politician and that there were five possible diagnoses of his condition - with test results becoming available in two days.

Dr Murakhovsky also said that there are many legal questions to be resolved before the Russian opposition leader can be handed over to European doctors.

Britain's Foreign Secretary Dominic Raab previously said he was "deeply concerned" about the reported poisoning, adding: "My thoughts are with him and his family."

And French President Emmanuel Macron offered France's help, saying: "We are clearly ready to provide all necessary assistance to Alexander Navalny and those close to him in terms of healthcare, in terms of asylum, and protection, that is clear. I hope he can be saved."