Russian opposition figure Alexei Navalny is unconscious in hospital suffering from suspected poisoning, his spokeswoman has said.
The anti-corruption campaigner fell ill during a flight and the plane made an emergency landing in Omsk, where doctors said he was in a coma and they were trying to save his life.
His team suspects something was put in his tea at an airport cafe. The Kremlin said that it wished Mr Navalny a “speedy recovery”.
Mr Navalny, 44, has for years been among President Vladimir Putin’s staunchest critics.
In June he described a vote on constitutional reforms as a “coup” and a “violation of the constitution”. The reforms allow Mr Putin to serve another two terms in office, after the four terms he has already had.
British Foreign Secretary Dominic Raab said he was “deeply concerned” by the reports Mr Navalny had been poisoned, and sent his thoughts to him and his family.
What has the spokeswoman said?
Kira Yarmysh, the press secretary for the Anti-Corruption Foundation, which Mr Navalny founded in 2011, tweeted: “This morning Navalny was returning to Moscow from Tomsk.
“During the flight, he felt ill. The plane made an urgent landing in Omsk. Alexei has toxic poisoning.”
She added: “We suspect that Alexei was poisoned by something mixed into [his] tea. It was the only thing he drank since morning.
“Doctors are saying that the toxic agent absorbed faster through the hot liquid. Right now Alexei is unconscious.”