Another Russian, skeleton athlete Pavel Kulikov, has also admitted to having tested positive for the recently banned substance, while Slovakian wrestler István Lévai is another to have failed.

Kuksenkov, who won the national individual all-around title in Pensa on Friday (April 1) before withdrawing the following day, was part of gold medal-winning teams at the 2014 European Championships in Sofia and the 2015 European Games in Baku.

He also claimed team, all-around and pommel horse gold medals at the 2013 Summer Universiade in Kazan, just a year after switching nationality from Ukraine, for whom he had competed under the name Mykola Kuksenkov.

The Kyiv-born 26-year-old had earlier won European bronze medals in 2009 and 2011 for his country of birth.

According to Russian national coach Valentina Rodionenko, he failed despite not having taken meldonium since August.

"As yet, no one knows how long a period is needed for meldonium to leave the body," she told the TASS news agency.

"It's a kind of wild, wrong situation, which needs to be sorted out with joint effort."

Meldonium was moved from the monitored to the prohibited list by the World Anti-Doping Agency on January 1 due to "evidence of its use by athletes with the intention of enhancing performance".

Kuksenkov becomes the first confirmed failure in the sport of gymnastics, but 25 Russians are now known to have failed, including two sambo players who are yet to be named.

The list, headed by tennis superstar Maria Sharapova, also includes skeleton bobsledder Kulikov, who admitted in a statement to have failed after finishing 12th at February's World Championships in Igls.

He also claims to have stopped taking the substance last August.

Other nations have also been hit, with the International Weightlifting Federation having announced yesterday that double world champion and two-time Olympic silver medallist Andrei Rybakov of Belarus had recorded a positive test. 

Wrestler Lévai, a Hungarian-born Slovakian who won under 66 kilograms Greco-Roman bronze at Baku 2015, has also admitted to having failed.

He claims to have stopped taking the substance once it was added to the banned list at the beginning of the year.

List of Russians known to have tested positive for meldonium