Six Northern Ireland fans hurt in pub clash as they drank with Polish fans
It's believed that six Northern Ireland fans were injured during a clash with French locals in a Nice bar.
However, the violence involving a small number of Northern Ireland fans in France was short and minor, police said.
Northern Ireland fans claimed on social media that the trouble was caused by 20-30 French hooligans as they mixed sociably with Polish fans in a bar.
One Polish fan was also injured.
The French troublemakers created the problem in the south coast city of Nice around 11pm Saturday night but there was no fighting with supporters of Sunday's opponents Poland, the Police Service of Northern Ireland (PSNI) said.
Supt Nigel Goddard said: "It is disappointing that a small number of Northern Ireland fans responded but it was only a short and minor incident."
It is understood a small number of supporters were injured during the face-off near the Place Massena.
French riot police were called in to disperse local "ultras" who attacked the Northern Ireland football fans, a senior supporters' representative said.
Gary McAllister, chairman of the Northern Ireland supporters' clubs, tweeted: "Local ultras attacked Polish and NI fans who were mixing well.
"French riot police dispersed locals."
Thousands of Northern Ireland and Poland fans have converged on the city on the Mediterranean coast for Sunday's fixture.
There were noisy but peaceful scenes throughout Saturday and many examples of friendly banter between the two sets of supporters.
Revellers partied into the small hours in the area around the Place Massena under the watchful eyes of French police.