The former International Olympic Committee president Juan Antonio Samaranch is gravely ill with severe heart problems.
A spokesman for the Barcelona hospital where the 89-year-old is being treated says his condition is very serious.
The Spaniard was widely regarded as the most powerful man in sport when he headed the IOC from 1980 to 2001.
An astute figure on the global stage, he oversaw the commercialisation of the Olympics as athletes were finally allowed to embrace professionalism.
Only Pierre de Coubertin, the "father" of the modern Olympics and IOC chief from 1896 to 1925, held the post for a longer period.
In recent years he was a key part of Madrid's failed bids to host the Olympics in 2012, which London eventually won, and 2016, which went to Rio de Janeiro.