The health of Russian leaders has traditionally been a subject shrouded in secrecy, going back to the early years of the Soviet system.

President Yeltsin has had heart problems for more than ten years but the seriousness of his condition only became apparent on the eve of his re-election in 1996 when he had a series of heart attacks and underwent multiple bypass surgery.

Since then he's had recurring respiratory problems.

The president recently gave up day to day running of the country to the prime minister, Yevgeny Primakov.

But he rejected any suggestion of stepping down before the end of his term, in the year two-thousand.

The Russian parliament sought unsuccessfully to make him undergo a medical test to determine whether he is capable of continuing in office.