The chess grandmaster was defending his titles at the Fide World Rapid and Blitz Chess Championships in New York when the incident happened.

Officials said Carlsen had broken the dress code regulations by wearing jeans, but when they asked him to change, he refused.

Fide, the governing body said it had issued the reigning champion with a US$200 fine.

Carlsen, who was world champion between 2013 and 2023, said he had a lunch meeting prior to the round and had to get changed quickly.

“I put on a shirt, jacket and honestly I didn’t even think about jeans, even changed my shoes,” he said.

“I didn’t even think about it… First of all, I got a fine which is fine, and then I got a warning that I would not be paired if I didn’t go change my clothes. They said that I could do it after the third round today.

“I said ‘I’ll change tomorrow if that’s OK, I didn’t even realise it today’, but they said, ‘Well you have to change now’. At that point it became a bit of a matter of principle for me.”

The world number one said he would not appeal the decision, adding: “Honestly, I am too old at this point to care too much.”

In a cheeky post on X later, Carlsen shared a photo of his jeans and jacket combination and wrote “OOTD” (outfit of the day).

In a statement, Fide said that its rules were applied “impartially”, citing another case where a player was fined before changing his shoes.