Poland summoned the Dutch ambassador on Saturday claiming that the arrest of Legia Warsaw players after a European match may have been motivated by prejudice against Poles.
It was the latest round of a spat between the countries that began when Dutch police arrested two players from the Polish club amid violent scenes at a Europa Conference League clash in Alkmaar on Thursday.
The Polish foreign ministry said on Saturday that "unacceptable situations have arisen in which Polish spectators, supporters, officials and players of the Legia Warsaw club have been subjected to physical and verbal abuse".
"It is clear from the unequivocal testimony of the victims that the actions of the mayor of Alkmaar and the local police in particular can be interpreted as being characterised by national prejudice," the ministry said in a statement after the meeting in Warsaw with ambassador Daphne Bergsma.
Dutch police said in a statement on Friday that they had arrested the players after they had assaulted two AZ Alkmaar staff members "to such an extent that they needed medical attention".
The two Legia Warsaw players, reportedly Portuguese midfielder Josue Pesqueira and Serbian centre-back Radovan Pankov, were released later Friday but remain under investigation, the police said.
The confrontation took place when the Dutch police blocked the Legia team bus "for the players' own safety" because visiting fans were still being escorted from the ground after the game, which AZ Alkmaar won 1-0.
"A number of players and officials apparently disagreed with this and started to become violent," Dutch police said.
Riot police boarded the bus and took the two players into custody.
"An arrest is a serious measure, the police do not do this without reason. Certainly not with players after an international match," the Dutch police said.
Polish media reported that the police stormed the bus, pinned club president and owner Dariusz Mioduski to the ground and smashed his phone as he was recording events.
Mioduski has described what happened as "an absolute scandal".
"The team is shocked by what happened because no one has experienced anything like this before," he said.
Dutch police said violence broke out before the match, with Legia Warsaw fans storming the entrance to the ground and knocking one officer unconscious.
Police used tear gas to disperse the visiting fans.
The Dutch authorities said they had told Legia Warsaw they would not be able to police the game safely due to other events in the city and had appealed to the Polish club to keep its fans at home.
"During match day, it became clear that Legia Warsaw had not stuck to this agreement," the police said.
It's a game of football
With elections looming in both countries, the spat quickly escalated to the political level.
Polish Prime Minister Mateusz Morawiecki described the events as "very worrying" and called for an investigation, insisting that Polish supporters should be "treated according to law".
Deputy Foreign Minister Pawel Jablonski added that his office was looking into whether "the Dutch police and AZ Alkmaar staff broke the law in relation to Polish citizens... due to their nationality and their use of the Polish language".
The Polish football federation has asked their Dutch counterparts and UEFA for explanations.
"The Polish media paints the picture that players were victims of riot police actions, but this is by no means the case. It was the players who used violence," Dutch police said.
Dutch Justice Minister Dilan Yesilgoz-Zegerius said her main concern was the injured police officer and she criticised the travelling fans.
"It's a game of football. So behave and don't lean on the police. The aim is to have fun," she said.
She dismissed the criticism from Morawiecki, saying: "I would prefer he looked at his own club first."
