The 2021 world champion Abuladze has "liked" a series of Ivkin's Instagram posts that show him taking part in the invasion of Ukraine.

Ivkin is a judo coach but joined the Russian forces last year after the war began.

The pair have also shared conversations on the social media platform with Abuladze giving his backing to Ivkin's presence in Ukraine, who responded by saying that he often shows Abuladze's videos to the children he trains.

"Another Russian war criminal turned out to be a friend of the Russian participants of the World Judo Championship," read a statement from Base of Ukrainian Sports.

"Nikita Ivkin is a master of sports and judo coach who volunteered to go to the territory of Ukraine last year to kill women, children and civilians."

Abuladze won gold at the 2021 World Judo Championships in Budapest as he prevailed in the men's under-60-kilograms category.

He also competed in this year's event in Doha last month but failed to reach the podium.

The International Judo Federation (IJF) was initially one of the few International Federations who permitted Russian and Belarusian athletes to compete as neutrals after the full-scale invasion of Ukraine, contrary to the International Olympic Committee (IOC) recommendations at the time.

However, the IJF introduced an outright ban in September last year which ran through to January 2023 after Russia pulled out of the World Championships in Uzbekistan's capital Tashkent.

The lifting of this ban preceded updated IOC recommendations in March which cleared the way for Russian and Belarusian athletes to compete in international sport as neutrals, provided they do not support the war in Ukraine and are not affiliated to the military.

insidethegames has contacted the IJF for comment.