Story highlights Vladimir Kara-Murza blames poison for illness that appeared suddenly in 2015

Kremlin has denied involvement in the past illness; lawyer says he has no evidence of poisoning

Moscow (CNN) A critic of Russian President Vladimir Putin who was in a coma in 2015 after a suspected poisoning has been hospitalized in Russia after falling ill in the early hours of Thursday, his attorney said.

Vladimir Kara-Murza has suffered "multiple organ failure," is on dialysis and is being artificially ventilated, his lawyer, Vadim Prokhorov, wrote on Facebook.

Kara-Murza, 35, is "currently in a stable but critical condition" in a hospital, Prokhorov said by phone. "It is a very, very difficult situation," he added.

Prokhorov said he doesn't believe this illness is related to Kara-Murza's previous health problems, but said he suspects it is another case of poisoning.

"None of the medical staff can explain the reason for his current condition. Both last time and once again now," he said.

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