His death was announced by the Russian Artistic Gymnastics Federation.

"It's hard to believe - another nine-time world champion, Honoured Master of Sports of the USSR, a legend of world gymnastics has gone into the world," the governing body said on its website.

"This is a great loss, we offer our condolences to the family, friends and the entire artistic gymnastics community."

Korolev won three gold medals at the 1981 World Gymnastics Championships in Moscow in the team, all-around and floor exercises, along with a bronze in the pommel horse.

After winning only a silver medal in the team event at Budapest 1983, he returned to his best form for the 1985 World Championships in Montreal.

He won gold medals again in the team and all-around but added the rings and vault with silver in the floor exercise.

In Rotterdam two years later, Korolev won the team and rings, adding another silver in the all-around.

Korolev also won 13 medals at the European Gymnastics Championships, including five gold.

His hopes of competing at the 1984 Olympic Games in Los Angeles were dashed by the Soviet-led boycott.

Korolev missed Seoul 1988 because of an Achilles tendon injury.

In between, at the 1986 Goodwill Games in Moscow, he won five gold medals and a silver.

Korolev retired in 1989 with a total of 34 individual medals at World Championships, World Cups, and European Championships competitions.

He Is widely regarded as the most decorated non-Olympian - male or female - gymnast of all time.

After his retirement, Korolev worked as a coach at the Tolkachev Children's and Youth Sports School in his hometown Vladimir, 120 miles east of Moscow.

He died on April 29.