Serbia's refusal to allow boxers from Kosovo into the country for the men's world championships was due to international federation AIBA's lack of due diligence in awarding the tournament to Belgrade, the International Olympic Committee said on Sunday.
The Kosovo delegation said it was twice refused entry into Serbia at the border on Saturday, initially because of the national symbols on their equipment, and again later in the day, even though they had removed them.
Serbia, which lost control of Kosovo in 1999 after a NATO bombing campaign, does not recognise Kosovo as a state after it declared independence from Serbia in 2008.
The IOC said the incident was triggered by AIBA's failure to follow advice from the IOC when awarding a major event.
"It appears that AIBA has not applied the necessary due diligence before allocating this tournament to Belgrade, despite the fact that the IOC has repeatedly advised the international federations of the necessity of such due diligence," an IOC spokesperson said.
AIBA said it believed all athletes should receive a fair chance to compete.
"AIBA aims to provide a welcoming home for every boxer, and the world of boxing has no borders," it said on Saturday. "Sport is intended to unite people and should be free of national politics.
"AIBA is in contact with the event host for the AIBA World Championships, the Serbian Boxing Federation, in an attempt to remedy the situation."
The IOC suspended AIBA in 2019, stripping it of any involvement in Olympic qualifiers and the Tokyo 2020 Games tournament over a string of governance, finance and ethical issues.
It has urged immediate and wide-ranging reforms is to conduct a review of them to assess the status of the suspended federation.
"Therefore this incident, which is detrimental to the athletes of Kosovo, adds to the grave concerns that the IOC has with regard to the governance of this suspended International Federation," the spokesperson said.
The IOC officially recognised Kosovo in 2014 even though it is not yet a member of the United Nations, its membership blocked by Russia, Serbia's traditional ally.
Kosovo has taken part as an independent nation in both the 2016 and the 2020 summer Olympics.