Vladimir Kara-Murza, a known critic of Russian President Vladimir Putin, has left Russia along with his wife Evgenia Kara-Murza and his doctor to seek medical treatment. Kara-Murza has suffered from repeated poisoning in the past and his wife has blamed the Kremlin for this. Vadim Prokhorov, Kara-Murza's lawyer, confirmed this in a Facebook statement.

Kara-Murza, who went into a coma two years ago, was hospitalized early this month in Moscow for suspected poisoning, but was recently discharged. Prokhorov did not reveal where Kara-Murza is headed, but said his client vowed to pursue the restoration of Russian democracy through civil rights reforms and free press.

Kara-Murza is part of an anti-Putin organization known as Open Russia. It was founded by former oil tycoon and now activist Mikhail Khodorkovsky, who got a 10-year jail term after openly criticizing Putin.

Kara-Murza's illness was diagnosed by his doctors as something related to toxic substances, according to CNN. He became ill four months after the assassination of his friend Boris Nemtsov near the Kremlin in February 2015. Kara-Murza lives in Virginia with his family, but was in Russia to promote a documentary on Nemtsov' assassination.

"Vladimir Putin does not deserve any benefit of the doubt here, given how commonplace political assassinations and poisonings have become under his regime," United States Senator Marco Rubio said. "I am praying that Kara-Murza's condition improves," he added.

Kara-Murza's health has been deteriorating in the past two years since his first reported poisoning, according to MSN. His laboratory results show his blood had high levels of heavy metals. His request for an investigation on the poisoning incident was, however, denied by the Russian Investigative Committee.

Kara-Murza is not only an anti-Putin activist, but is also among those actively pushing for the Magnitsky Act expansion in the United States, also known as the Global Magnitsky Human rghts Accountability Act. The bill authorizes the US president to ban entry and impose property sanctions against foreign persons who have committed extrajudicial killins or other gross human rights violations.