Putin opponent Alexei Navalny poisoned by 'toxin' in his tea - reports

Alexey Navalny is reported to be unconscious in hospital, suspected of having beeen poisoned by a toxin in his tea. Photo / Getty Images

Prominent Russian anti-corruption activist and Vladimir Putin opponent Alexei Navalny has reportedly been admitted to hospital in an unconscious state after being reportedly poisoned by a "toxin" in his tea.

The 44-year-old foe of Russian President Vladimir Putin felt unwell on a flight back to Moscow from Tomsk, a city in Siberia, Kira Yarmysh said on Twitter.

"This morning Navalny was returning to Moscow from Tomsk. On the flight he started feeling ill. The plane made an emergency landing in Omsk. Alexei has been poisoned with a toxin. Right now we're in an ambulance on the way to the hospital," his press secretary tweeted.

She later added that Navalny is in the ICU.

"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. Right now Alexei is unconscious," she added.

According to Yarmish, this is not the first time Navalny has been poisoned.

Last year, while in a detention centre, he was reportedly victim of poisoning as well.

He 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 then said he had a severe allergic attack and discharged him back to prison the following day.

"Obviously, now they've done the same thing to him again," she added.

The politician is in grave condition, Russia's state news agency Tass reported, citing the chief doctor at the hospital.

The Daily Beast reports that the latest poisoning happened just weeks after Navalny levelled corruption accusations against a Kremlin environmental inspector, Svetlana Radionova.

He cited documents tying Radionova to luxury real estate in both Moscow and Nice, saying "such wealth cannot be explained".

"It is so outrageous," Navalny said in a clip on YouTube, viewed by more than three million people.

- with AP