A Kremlin spokesman announced he had gone to the Barvikha sanatorium to recuperate, a day after doctors ordered him to cancel a trip to the European Union summit in Austria because of "unstable blood pressure" and extreme fatigue.

The renewed health scare coincides with the crucial summit where Prime Minister Yevgeny Primakov has been standing in for the Russian president.

Mr Primakov set out Russia's plans to pull the country out of its economic crisis and discussed how western Europe could help in his talks with the Austrian Chancellor, Viktor Klima, who is the current head of the European Union and the president of the EU Commission, Jacques Santer,

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The two sides issued a statement. after the talks affirming that the programme Russia required, to address its pressing social and financial needs, must be credible and sustainable.

Deja-vu

Mr Yakushkin said the Russian president will undergo "a recuperation course" at the sanatorium, which he has visited in the past. He spent time there following multiple heart bypass surgery in 1996.

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The Kremlin spokesman earlier announced Mr Yeltsin had developed "asthenia" - a condition involving physical and psychological exhaustion.

"[The doctors] were unanimous about cancelling the trip," Mr Yakushkin was quoted as saying.

Yeltsin era 'over'

At the weekend, Mr Yeltsin's spokesman insisted his condition was normal for a man of his age and the president was fed up with the rumours about his health.

Austrian Chancellor Viktor Klima met Yevgeny Primakov instead

But Russian opposition forces, who this autumn have intensified their calls for Mr Yeltsin to step down, pounced on the latest opportunity.

Communist Party leader Gennady Zyuganov said: "The Yeltsin era is over. We should speak of it less and less.

"We cannot look at him without being shocked. The best thing for Russia would be that Mr Yeltsin stands down, but he does not have the will to do that."

Another Communist, Vitkor Ilyukhin, said: "Mr Yeltsin can only hold a conversation for a few minutes, then his speech becomes confused and he repeats himself."

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Mr Yeltsin has rarely been seen since the start of Russia's financial crash in late August.

The BBC's correspondent in Moscow, Robert Parsons, says that to all intents and purposes the government of the country has passed into the hands of Mr Primakov.