Updated

Former Russian Prime Minister Yegor Gaidar was released from a Moscow hospital Monday evening following a mysterious illness, his spokesman said.

Doctors could give a final diagnosis of what struck the 50-year-old economist as early as Tuesday morning, spokesman Valery Natarov told The Associated Press.

Gaidar -- who served briefly as prime minister in the 1990s under President Boris Yeltsin and is a leader of a Russian liberal opposition party -- began vomiting and fainted during a conference in Ireland on Nov. 24, and was rushed into intensive care at a hospital.

He fell ill a day after ex-KGB officer and Kremlin critic Alexander Litvinenko died in London after being poisoned with the radioactive element polonium-210.

Gaidar's aides said doctors treating him in Moscow suspected he had been poisoned were working to determine how that might have happened. Irish doctors concluded he was not poisoned by a radioactive substance, but said his health had suffered sudden "radical changes."

Gaidar's illness added to growing speculation in Moscow over Litvinenko's death and who might be responsible.

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