Police made four arrests after a group of about 100 men assaulted customers at a pub near Wembley Stadium before England's match with Germany on Monday.
A number wore England hats and scarves but the Metropolitan Police says they are "believed to be German fans".
The group, many of whom were wearing masks, entered the Green Man pub at 17:50 BST and started attacking fans.
Three people suffered serious leg, wrist and thumb injuries and were treated at the scene.
Others sustained head and facial injuries but none are believed to be in a life-threatening condition.
the group were carrying weapons, including machetes and knuckle-dusters, but this has not been confirmed by police.
The trouble lasted for two minutes before the group fled when officers responded.
The Met Police has told the BBC a plan was in place to deal with any issues involving fans and no other reports of disorder around the game had been made, while enquiries are still ongoing.
In a statement, they said: "At 17:50hrs on Monday, 26 September a group of approximately 100 males, many wearing masks, approached a pub in Dagmar Avenue, Wembley through an alley leading towards the car park.
"While a number of the group were wearing England hats and scarves, it is believed they were German 'fans'.
"The group entered the beer garden of the pub and began assaulting customers, most of whom were in the area to attend the England vs Germany match. Punches and projectiles including traffic cones were thrown."
Gareth Southgate's side came from two goals down to lead 3-2 before Germany equalised late on in England's final game before the World Cup begins in Qatar in November.
Football Policing Lead chief constable Mark Roberts told the BBC: "This isn't just in the UK. We speak to police and colleagues across Europe and Uefa and it's being seen across the continent."