UEFA have vowed to crack down on racism at the European Championship after acknowledging Holland's black players were abused during a training session in Krakow.
Members of Bert van Marwijk's European Championship squad were allegedly subjected to monkey chants at Wisla Krakow's Miejski Stadium on Wednesday, with captain Mark van Bommel branding the incident "a real disgrace".
Having been satisfied by the Dutch Football Association's initial assurances the abuse was not racially-motivated, UEFA announced on Friday morning they had been made aware of "isolated incidents of racist chanting".
European football's governing body confirmed they would consider increasing the number of stewards at open training sessions in order to eject fans if there was a repeat. They said in a statement: "UEFA has now been made aware that there were some isolated incidents of racist chanting that occurred at the open training session of the Dutch team.
"UEFA has not yet received any formal complaint from the KNVB.
"Should such behaviour happen at further training sessions, UEFA would evaluate the operational measures to be taken to protect the players.
"UEFA has a zero-tolerance policy when it comes to discriminatory behaviour and has given the power to referees to stop matches in case of any repeated racist behaviour."
Press Association Sport understands UEFA's statement followed lobbying from the FARE network.
The chief executive of European football's leading campaign group against racism, Piara Powar, earlier told Press Association Sport: "If the captain says, 'My team-mates were racially abused, I heard it, I was there at the ground level', then one expects any FA to back the captain. We're very clear with UEFA that any incident of this kind needs to be looked at."
Powar called on teams to play their 'open' training session behind closed doors if necessary. He said: "Public displays of intolerance like this - xenophobia, anti-semitism and racism - can't be allowed to go on. If that means playing behind closed doors and closing down that whole open-training system then I think that needs to be done."