Van der Poel soloed to victory to deny Belgium’s Wout van Aert a fourth successive world title and cap off a dominant cyclo-cross campaign. It was the Dutchman's second elite men's World Championship victory following his 2015 triumph.
After the race, however, his father Adrie van der Poel complained that Belgian supporters had doused his son in beer during the event. An image circulated on social media after the race depicted a spectator showing his middle finger to Mathieu van der Poel as he rode past.
In a statement issued on Monday evening, the Belgian cycling federation decried the behaviour of some spectators and congratulated Van der Poel on his victory.
"Belgian Cycling strongly supports the internationalisation of cyclo-cross. That is why it is regrettable that one had to witness that a certain number of spectators – fortunately an absolute minority – are not of the same view. Nobody, including the Belgian delegation, benefits from unsporting and insulting behaviour," read the statement.
"The fact that our riders had to let the title go to Mathieu van der Poel on Sunday afternoon, after a fair sporting battle, is part of the laws of sport. For Belgian Cycling, the Dutchman deserved the title. We sincerely congratulate Mathieu van der Poel, not only for the way in which he won his second world title, but for all of his fine performances these past months."
Van der Poel beat four Belgian riders to the title on Sunday, as Van Aert took second place ahead of Toon Aerts, while Michael Vanthourenhout and Laurens Sweeck completed the top five.
"The majority of Belgian fans who travelled to Denmark made the World Championships in Bogense a popular party,” concluded the Belgian Cycling statement. “It is unacceptable that a few people partly spoiled that unique atmosphere, and so Belgian Cycling wishes to apologize for this."
The Cyclo-cross World Championships were first held in 1950 and French claimed the first nine titles. Belgium only emerged as a force when Eric De Vlaeminck landed his first title in 1966, but the country has been largely dominant in the intervening period, amassing some 30 elite men's rainbow jerseys over the years. Since 1998, at least one Belgian rider has finished on the podium of the elite men's Worlds every year.
Elite women's champion Sanne Cant was Belgium's lone rainbow jersey winner in Bogense, however, and the country placed behind both the Netherlands and Great Britain in the final medals table.