Ukrainian boxer Oleksandr Usyk was released Wednesday after being detained at Krakow airport in southern Poland.
A video on social media showed Usyk being detained and handcuffed by security forces at the airport.
The 37-year-old was released after what he referred to as a "misunderstanding," but gave no further details.
The reasons for this incident are unknown, but the boxer’s wife Yekaterina posted a message on Instagram stresing that everything was fine and that "Oleksandr will explain everything later," and that the case has no criminal overtones.
But Volodymyr Zelenskyy, Ukraine’s president, wrote that he was outraged by such behavior towards the Ukrainian champion and instructed top officials at the Foreign and Interior ministries to "carefully and thoroughly" investigate the incident.
Zelenskyy concluded a message by stating that "he was politely informed that everything is in order and that Usyk has been released and no one is holding him."
The heavyweight world champion thanked people for their "concern" after he was detained at the airport.
Usyk became undisputed champion in May when he beat Tyson Fury. He is undefeated and seen as the world's best heavyweight, holding the WBC, WBO and WBA belts.