President Yeltsin cancelled engagements and vanished to one of his country residences yesterday with what officials variously called a sore throat, flu and a severe respiratory infection.
As financial markets worldwide dipped at news of the chronically unwell president's latest illness, his press spokesman said Mr Yeltsin (67) might still take part in next week's meeting of leaders of former Soviet countries in Moscow.
His latest illness came three days after he ostentatiously touched wood in the Kremlin, afraid he had tempted fate by bragging about how healthy he was. On that occasion he challenged journalists to test his fitness. "I'll meet you in the pool, on the tennis court, on the running track. Come on!" Mr Yeltsin said.
Shortly afterwards he began coughing and on Wednesday he apologised at the beginning of a speech for being hoarse.
Mr Yeltsin has retreated for a course of antibiotics to the presidential estate at Gorky-9, outside Moscow, within a few minutes drive of key medical centres like the Barvikha sanatorium and the Central Clinical Hospital.
The Prime Minister, Mr Viktor Chernomyrdin, who according to the constitution takes over as caretaker head of state if the president is incapacitated or dies, is in the US, leaving Mr Anatoly Chubais, his unpopular liberal deputy and currently a key figure in a long-running media smear war, to run the government.
Mr Chubais stood in for the president yesterday at a reception for German parliamentarians.
Seamus Martin adds: Announcements from the Kremlin on Mr Yeltsin's latest illness, particularly statements referring to laryngitis, bear a strong resemblance to those issued in June 1996 prior to the second round of Russia's presidential election.
On that occasion Mr Yeltsin went missing for a week and failed to show up at a polling station where journalists had been brought to see him cast his vote. Kremlin spokesmen at the time issued statements that the president was suffering from a cold and had lost his voice through an attack of laryngitis. It was later learned that Mr Yeltsin had suffered a heart attack, though many observers felt at the time that his loss of speech was probably the result of a mild stroke. In November 1996 he underwent open heart surgery in a quintuple bypass operation. He is understand to have been warned to cut down on his consumption of alcohol at that time.
Health problems have dogged Mr Yeltsin for a number of years along with reports of consistent heavy drinking. He is known to have had at least three heart attacks and may have had more. In September 1994 when he failed to get off his aircraft to meet the then-Taoiseach, Mr Albert Reynolds, at Shannon he gave the excuse that his guards had forgotten to wake him up. In his memoirs, however, Gen Alexander Korzhakov who was on the plane with Mr Yeltsin has written that the president suffered a heart attack at that time.
Mr Yeltsin was admitted to a sanatorium with a chest infection in December of last year and only three days ago issued a statement which said he was in perfect health.