England’s opening Euros game against Serbia has been marred by violence, with the arrest of seven Serbs and a warning of banning orders for any UK nationals found to be involved.

A brawl on the terrace of a restaurant in the west German city of Gelsenkirchen left one police officer and a number of fans bloodied, although it was unclear who instigated the incident.

Video footage on social media brought back memories of previous shameful episodes for English football with chairs, bottles and tables seen upended on the terrace of a restaurant where a large Serbian flag had been put up.

A spokesperson for the German police said that “the two fan groups had been separated” and that “seven Serbian citizens were taken into custody during the clashes”.

The spokesperson added: “There was also a complaint of grievous bodily harm. The background to this is still unclear.”

Some witnesses claimed that the main instigators had been Albanian fans, although the German police said they were unable to confirm the nationalities of any of those who took part.

A UK football policing unit spokesperson said: “We are aware of an issue in Gelsenkirchen ahead of the England v Serbia match. Our German colleagues have made a number of arrests of what we currently believe to be Serbian supporters. At this stage we do not believe that any UK nationals have been arrested but inquiries are ongoing.

“Our officers are at the location speaking to German colleagues. Our investigation team is now reviewing footage of the incident and if any UK nationals have been involved, football banning orders will be sought.”

One police officer was treated for a head wound and an undisclosed number of fans were seen by medics after hooligans rampaged outside the Hirt Steakhouse where Serbia supporters had been drinking five hours before the game.

“Chairs, bottles, everything you can imagine suddenly came down,” said one eyewitness. Many of the perpetrators of the violence are understood to have fled the scene as about 200 German riot police arrived.

Those who provoked the violence had been seen by British police “spotters” rushing towards a bar in which about 30 Serbia fans were enjoying a drink five hours before the kick-off of England’s first game.

About 200 officers sealed off the area after the perpetrators fled while smaller squads of riot police were despatched to hunt down those involved.

A spokesman for Gelsenkirchen police said: “We can confirm that there was a physical altercation between several people in the south of the city of Gelsenkirchen.

“We cannot confirm at this point whether the altercation was football related or which nationalities were involved.”

More than 30,000 England fans – only 20,000 of whom are believed to have tickets – were in Gelsenkirchen for the game with Serbia.

The match had been designated as “high risk” due to the reputation of the two fanbases, with the police last week warning that up to 500 Serbian hooligans bent on violence could seek to cause trouble.

The game was otherwise peaceful, however, with a heavy German police presence keeping the Serbia and England fans apart on Sunday.

Fans instead complained of the difficulty in making the 15-minute tram journey from the city centre to the Arena AufSchalke stadium. Hundreds of fans were left walking miles as they found themselves unable to get on a shuttle bus or tram to the venue.

British police have been working in close cooperation with their German counterparts, with undercover spotters from both nations working among the supporters drinking in the bars around Gelsenkirchen in west Germany.

There has been an uptick of football disorder in recent years in England and Wales related to domestic matches, leading to concerns that such behaviour could spill over into internationals.

A downward trend in terms of the number of arrests at domestic football games has been sharply reversed post-Covid, with the number now at the heights of a decade ago.

As of August 2023, there were 1,624 football banning orders in force, an increase of 24% compared with the year before. Within the 2022-23 season, 682 banning orders were issued, an annual increase of 32%.

All those under banning orders have had to surrender their passports for the duration of the tournament in Germany.