The Investigative Committee accused Navalny of slandering a war veteran showing support for a controversial referendum.
An air ambulance is on its way from Germany to collect Russian opposition politician Alexey Navalny who is fighting for his life in a hospital in Siberia after falling ill from suspected poisoning during a flight to Moscow.
Spokesman Kira Yarmysh said Navalny, 44, was flying from Siberia to the Russian capital on Thursday after a work trip to Tomsk when his plane was forced to make an emergency landing after he fell ill.
He is in a coma and on a ventilator in the intensive care unit for toxicology patients in Emergency Hospital No 1 in the Siberian city of Omsk, according to the TASS state news agency.
An ambulance aircraft with a team specialised in treating coma patients was reported to have left Germany early on Friday morning to collect Navalny. AFP reported at 04:32 GMT that the plane had taken off.
In an earlier statement, the Berlin-based Cinema for Peace Foundation said the air ambulance was being deployed at the request of Pussy Riot’s Pyotr Verzilov and it was equipped with medical equipment and specialists.
The leaders of both Germany and France have expressed their deep concern about Navalny’s condition and offered assistance.
At a joint news conference, French President Emmanuel Macron said France was ready to provide help in relation to Navalny’s treatment, asylum or protection while German Chancellor Angela Merkel said the Russian opposition politician could get treatment in either country.
Merkel said the news had truly “upset” her.
“I hope that he can recover and naturally whether it be in France or Germany he can receive from us all the help and medical support needed,” she said.
Earlier in Thursday, doctors gave contradictory information about Navalny’s condition, saying it had stabilised but also that there was still a threat to his life and they were working to save him.
“We think that Alexei was poisoned with something mixed in his tea. That was the only thing he drank in the morning,” Yarmysh wrote on Twitter.
“Doctors say the poison was quickly absorbed through the hot liquid.”
Navalny had drunk a cup of tea at a Tomsk airport cafe before boarding his flight, Yarmysh said.
The Interfax news agency quoted the cafe’s owners as saying they were checking CCTV cameras to try to establish what had happened.
Yarmysh told the Echo Moskvy radio station that Navalny was sweating on the plane and asked her to talk to him so that he could “focus on the sound of a voice”.
He then went to the toilet and lost consciousness.
“Alexei is still unconscious. He was put under ventilator. Police were called to the hospital on our demand,” said Yarmysh.
Passenger Pavel Lebedev posted on social media an account of what he saw.
“At the start of the flight he went to the toilet and didn’t come back. He started feeling really sick. They struggled to bring him round and he was screaming in pain.”
Tatyana Shakirova, a spokeswoman for the regional health ministry in Omsk, said: “The poisoning version is one of several versions being considered. It’s not possible now to say what the reason was.”
Yarmysh said she believed the suspected poisoning was connected to this year’s regional election campaign.
Kremlin spokesman Dmitry Peskov wished Navalny a speedy recovery, saying any poisoning should be confirmed by laboratory tests. He added that the government was ready to consider a request for Navalny to be treated abroad.
Navalny, known for his anti-corruption campaigns against top officials and outspoken criticism of President Vladimir Putin, has suffered physical attacks in the past.
Last year, Navalny was rushed to a hospital from prison where he was serving a sentence following an administrative arrest, with what his team said was suspected poisoning. Doctors said he had had a severe allergic attack and discharged him back to prison the following day.
He also endured chemical burns to his eye in 2017 when attackers threw green antiseptic at his face outside his office.
The charismatic lawyer and whistle-blower has been travelling the country to promote a tactical voting strategy to oppose pro-Putin candidates in more than 30 regional elections in September.
He has been the target of multiple criminal probes while his Anti-Corruption Foundation is regularly raided by police and investigators.
He has served numerous terms in police cells for organising protests.
Last month, the politician had to shut the foundation after a financially devastating lawsuit from Yevgeny Prigozhin, a businessman with close ties to the Kremlin.
The most prominent member of Russia’s opposition, Navalny campaigned to challenge Putin in the 2018 presidential election, but was barred from running.
Vyacheslav Gimadi, a lawyer with Navalny’s foundation, said the team is requesting Russia’s Investigative Committee open a criminal probe.
“There is no doubt that Navalny was poisoned because of his political stance and activity,” Gimadi said in a tweet on Thursday.
Former US ambassador to Moscow Michael McFaul tweeted: “Praying @navalny will be ok.”