President Yeltsin was admitted to a Moscow clinic after suffering a potentially serious brain spasm and not with a chill as officially claimed, Russian radio said yesterday, citing well-placed medical sources.
The condition had been brought on by general fatigue and overwork, said Moscow Echo radio, fuelling concern about Mr Yeltsin's health and sparking a prompt denial by the Kremlin.
"Boris Yeltsin had a severe spasm of the blood vessels in the brain, linked to sharp weather fluctuations and his general tiredness and overwork," the source said.
"After that, he genuinely suffered a chill but now his condition is improving," the source said, although it was not immediately clear when the spasm occurred.
Mr Yeltsin (66) would soon be able to take walks in the fresh air at the Barvikha clinic where he was admitted on Wednesday, provided his temperature remained stable, the source told the radio station. That prognosis chimed with a bulletin on the president's health released earlier by officials.
The Kremlin moved swiftly to dismiss the brain spasm report, saying: "This morning we published the bulletin by the medical panel on the president's state of health.
"There is nothing close to that (in the statement). We deny the report," a Kremlin spokesman said.
The Kremlin stressed that Mr Yeltsin would vote tomorrow in Moscow's municipal elections, even though the clinic was beyond the city limits. Doctors have advised Mr Yeltsin to remain at the clinic for 10-12 days.
A French neurosurgeon, who asked not to be named, said brain spasms could cause haemorrhaging of the brain lining, an extremely serious condition which can restrict blood supplies to the brain.
Another western doctor, who also asked for anonymity, said brain spasms were "a serious brain complaint".
The radio report came just hours after Kremlin officials said Yeltsin was in a "satisfactory" condition at Barvikha, following his admission with an acute viral infection and a slight temperature.
Mr Andrei Piontkovsky, director of the Moscow Centre for Strategic Studies, said the latest Yeltsin health scare would aggravate Russia's political and economic difficulties.
Mr Yeltsin had suffered problems with blood supply to the brain in the past, he said. "That explains his increasing incoherence recently, notably in Stockholm, where he was clearly intellectually unfit."
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