Moscow: Russian opposition politician Alexei Navalny was poisoned and hospitalised on Thursday morning, his spokeswoman said.

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

“The plane made an emergency landing in Omsk. Alexei has a toxic poisoning,” Yarmysh tweeted.

Navalny is unconscious and was placed on a ventilator in an intensive care unit. According to Yarmysh, he must have consumed something from the tea he drank this morning.

“Doctors are saying the toxin was absorbed quicker with hot liquid,” she said, adding that Navalny’s team called police to the hospital.

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

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