Moscow ? Another intriguing sickness: Former Russian Prime Minister Yegor Gaidar left a hospital Monday following a mysterious illness. Gaidar’s illness raised suspicions of another poisoning.

He fell ill a day after former KGB agent Alexander Litvinenko died in London from ingesting the radioactive element polonium-210. Gaidar’s aides initially said doctors treating him in Moscow suspected he had been poisoned and were working to determine how that might have happened.

Gaidar is a 50-year-old economist and leader of a Russian liberal opposition party who served briefly as prime minister in the 1990s under President Boris Yeltsin. He began vomiting and fainted during at a conference outside Dublin, Ireland, and was rushed into intensive care.

Some critics have tied both Litvinenko’s death and Gaidar’s illness to the October killing of Russian investigative journalist Anna Politkovskaya, also a Kremlin critic. Russia has denied involvement in Litvinenko’s death.