The Dutch national football squad was allegedly subjected to racial abuse at a training session in the Polish city of Krakow
Dutch national football team captain Mark van Bommel has branded the monkey chants directed to his team-mates during an open training session as "a real disgrace".
Van Bommel said: "You need to open your ears. If you did hear it, and don't want to hear it, that is even worse."
Uefa officials said an incident had occurred but it was a protest about Krakow not being given any Euro 2012 matches.
The news comes on the opening day of the tournament, which is being co-hosted by Poland and Ukraine.
The 16-team tournament kicks off this afternoon with co-hosts Poland playing 2004 winners Greece.
The Dutch players were reportedly targeted by Polish fans as they began their practice session at the Stadion Miejski.
Van Bommel responded by leading the squad to the far side of the pitch.
The abuse comes just a day after they had visited the Nazi concentration camp Auschwitz, which is nearby.
Van Bommel said: "It is a real disgrace, especially after getting back from Auschwitz, that you are confronted with this.
"We will take it up with Uefa and if it happens at a match we will talk to the referee and ask him to take us off the field."
This week Uefa president Michel Platini said referees have been instructed to call a halt to matches at this summer's tournament if a player is racially taunted.
However he also warned any player who left the field unilaterally in protest over abuse from the stands would be yellow carded.
Italy and Manchester City striker Mario Balotelli had earlier said he intended to do exactly that if he found himself being racially abused.