England football fans have been urged to behave responsibly ahead of their match with Wales at Euro 2016 later.
At least 36 people have been arrested following clashes in Lille on Wednesday – where riot police fired tear gas and charged at hundreds of England fans.
Martin Glenn, chief executive of the FA, said England fans should be aware of the “wider” situation in France, where police are facing terror threats.
Uefa this week threatened to disqualify England if there was any more violence.
Wednesday night’s disorder followed clashes between mainly English, Russian and French fans in Marseilles at the weekend.
England play Wales in Lens at 14:00 BST.
Thousands of English and Welsh supporters have been staying nearby in the larger city of Lille – where the latest disorder occurred.
Russian and Slovakian supporters have also been in Lille for their game at the city’s Stade Pierre-Mauroy, which took place on Wednesday.
The Russian football team were given a suspended disqualification from the tournament following attacks by their supporters on England fans in Marseille.
Speaking to BBC Radio 4’s Today programme, Mr Glenn said Uefa had focused on disorder blamed on Russian fans inside the stadium in Marseille when it issued the team with the threat of disqualification.
He said the atmosphere between England supporters and French police in Lille on Wednesday had seemed “to change overnight”.
‘Real security threat’
He called on England fans to show “consideration and respect”, pointing to the murder on Monday of two French police officials by a man claiming allegiance to so-called Islamic State (IS).
“The French are trying to deal with a real security threat,” Mr Glenn said.
“Behave responsibly, come and enjoy the game, but just have a think about the wider position.”
He said independent security experts had been in Lille and were due to report back to the FA later.
In a statement, tournament organiser Uefa said it “regrets the skirmishes which occurred in Lille last night”.
It added that police had been “quick to restore order and keep the situation under control”.
French authorities said those arrested on Wednesday included six Russians involved in the violence in Marseille.
Another five people were arrested for public drunkenness on a train from London that was stopped before it got to Lille and then allowed to continue.
Some English and Russian supporters had been detained after scuffles earlier in the day,
Hundreds of England fans were surrounded by riot police in the city’s main square before being pushed back into a corner of the square, which was then cleared.
BBC sports editor Dan Roan, who is with the England team, said concern about disorder would have “intensified” overnight.
England were now “skating on thin ice” in terms of the team’s participation in the tournament and the threat of disqualification will “inevitably” have an effect on the players, our correspondent added.
Six England fans, aged 20 to 41, have received jail sentences ranging from one to three months in relation to disorder surrounding the England-Russia game, which finished 1-1 on Saturday.
A drinking ban remains in place in some parts of central Lille and the stadium.
Shops selling alcohol in the city closed from 18:00 local time (17:00 BST) on Tuesday and will reopen at 06:00 (05:00 BST) on Friday.
Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways:
- Whatsapp: +44 7525 900971
- Send pictures/video to
- Upload your pictures / video here
- Tweet: @BBC_HaveYourSay
- Send an SMS or MMS to +44 7624 800 100