Ramzan Kadyrov, the head of the Russian republic of Chechnya, has been criticised for putting his three young sons into the ring to fight in a mixed martial arts (MMA) tournament on the eve of his birthday.

Kadyrov’s son Akhmad, 10, knocked out another boy on Tuesday in front of his father and a packed arena in Chechnya to win the “youth division” of the Grand Prix Akhmat 2016 international tournament.

Eli Kadyrov, nine, and Adam Kadyrov, eight, also won their bouts, the latter trading blows and grappling with his opponent before throwing him to the ground.

After the matches, which were broadcast by an MMA television channel, the brothers posed with huge gold title belts.

Kadyrov gushed about the fights on Instagram, but Russia’s most famous fighter and MMA union head, Fedor Emelianenko, called them “inexcusable”, saying MMA rules did not allow children under 12 to compete. He also noted that the boys were not wearing helmets or protective vests, and said fights held according to adult rules could harm children physically and psychologically.

“Children under 12 aren’t even allowed into the hall as spectators, but here kids who are eight years old were beating each other up in front of delighted adults. Is it really that important for everyone to organise a spectacle at the expense of children’s health?” Emelianenko wrote on his own Instagram.

President Vladimir Putin’s spokesman told journalists that the “knockout of a child, especially on television, is a reason for the appropriate oversight agencies to get involved”. The sports ministry told the news agency Tass that it would open an inquiry into the fights.

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Several Chechen officials responded to Emelianenko with insults and accusations. Timur Dugazayev, Kadyrov’s representative in Europe and general director of the leader’s Akhmat MMA promotion, said: “Fedor should look at the situation from a man’s point of view.”

MP Adam Delimkhanov, a relative of Kadyrov, said it was “strange to hear such words” from a fighter who “stole a win” after “losing shamefully and being harshly beaten” in his controversial June decision over Fábio Maldonado. Valid Edilov, director of the Akhmat fight club, accused Emelianenko of doping and argued that fighting was part of Chechen children’s upbringing.

Kadyrov was re-inaugurated as head of Chechnya on his 40th birthday on Wednesday after winning 98% of the vote in last month’s election. That same day, Russian state television broadcast the first episode of a show similar to Donald Trump’s The Apprentice, in which 16 people compete to become Kadyrov’s assistant. The contestants’ first task was to direct 3,000 Chechens in the stands of a football arena to hold up coloured placards and form the name of their team.