England fans have been warned not to "spoil the party" if they plan a belated World Cup arrival.
UK police issued the warning to stay-at-home fans who may be thinking of travelling to Russia after the Three Lions' free-scoring start to the tournament.
It comes after reports of a fight breaking out between football fans who were in Gdansk, Poland, on Wednesday night before travelling on to Kaliningrad for England's game against Belgium on Thursday night.
The National Police Chiefs' Council said trained police spotters witnessed a "scuffle" involving England fans, which was stopped by fellow supporters.
Gdansk police said they had received no reports of violence or made any arrested but those involved could face court action when they return home.
Two Belgium fans who witnessed the incident said it began after Germany were knocked out of the World Cup.
Claudio Swijsen, 38, from Genk in Belgium, said: "There were a lot of fans looking for trouble with the Germans because they lost.
"We make fun of them too but behind their back."
Jonathan Vermeeren, 37, from Hassell in Belgium, added: "They started fighting as well when the Germans lost, which was a bit crazy."
Chief Inspector Joe Stokoe, who is leading UK police on the ground in England's host cities, said: "It was reported to be a minor scuffle, self-policed by the fans themselves.
"But be assured we as UK police will follow that up and if there is any evidence of English fans contributing to any football disorder we will actively seek banning orders against those individuals."
Mr Stokoe said England fan's behaviour in Russia had been exemplary, except in one instance of anti-Semitic chanting in a bar in Volgograd after England's first game.
But he warned those thinking about travelling that they might find hotels and tickets are not "readily available".
Earlier this week, the Football Supporters' Federation told fans that it was not too late to join the World Cup party, after estimating the turnout against Tunisia was the lowest for 30 years.
Mr Stokoe said: "Other than that one abhorrent incident in Volgograd, we are not aware of any other incidents involving English fans.
"They took on board the message, they've come here to enjoy themselves, respect the country, respect the hosts, be good guests and make the most of this fantastic experience.
"Our message going forward would be remember that. Plan ahead.
"Think about if you're going to come to Russia, where you're going to stay, how you are going to get a ticket.
"It's not a country just to arrive in and take a chance.
"Do not just get a Fan ID, hop on a plane and land in Russia.
"I'm sure they would welcome you out here but think that through.
"Don't spoil the party, don't spoil all the good work done by English fans so far."