Putin critic Alexei Navalny 'unconscious' in hospital 'after being poisoned by toxic substance in his tea'

Russian opposition figure Alexei Navalny is "unconscious" in intensive care after a suspected poisoning, his spokeswoman has said.

Mr Navalny, 44, an outspoken critic of Russian president Vladimir Putin, was returning to Moscow by plane from Tomsk in Siberia when began to feel ill, his press secretary Kira Yarmish said on Twitter.

She said that he is believed to have been poisoned with a toxic substance in his tea.

She tweeted: “The plane made an emergency landing in Omsk. Alexei has a toxic poisoning.

“We assume that Alexei was poisoned with something mixed into his tea. That was the only thing he drank this morning.

"The doctors say that the toxin was absorbed more quickly because of the hot liquid."

Ms Yarmysh later tweeted that Mr Navalny was in intensive care, on a ventilator and still unconscious, and that the police had been called.

The opposition figure is a staunch critic of Mr Putin's United Russia and has previously described it as "the party of crooks and thieves".

In June, Mr Navalny slammed 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.

He has previously been jailed, including for taking part in protests over vote-rigging by Mr Putin's party.

He was also briefly jailed on embezzlement charges but denounced the sentence as political.

Mr Navalny wanted to stand in the 2018 presidential race but was barred because of previous fraud convictions.