"Earlier this afternoon there was a breach of security at Wembley Stadium, which resulted in a small number of people getting into the stadium without a ticket," the Metropolitan Police said.
"Officers worked closely with security officials to prevent any further breaches.
"We will also support action by Wembley Stadium officials to identify those without tickets and eject them."
A Wembley spokesperson added stadium stewards and security were working to remove the intruders.
"Anyone inside the stadium without a ticket will be instantly ejected," the spokesperson said.
Security staff were seen "rugby tackling people to the ground" inside the venue, a witness told Britain's domestic Press Association news agency.
At one point during the first half around 300 people were trying to get through, the witness reported to PA, with some supporters' tickets checked at half-time.
Meanwhile, footage posted to social media appeared to show scenes of violence on concourses within the stadium.
In one video lasting nearly a minute and a half, a large throng of men can be seen fighting -- throwing punches and kicks, some targeting people lying on the ground -- as just a couple of stewards attempt to intervene.
UGLY SCENES
The breach came as hundreds of ticketless fans tried to storm Wembley's outer gates in a bid to gain entry to England's contest against Italy.
Footage posted on social media showed supporters battling to get past lines of stewards and police as the atmosphere turned ugly in the hours before kick-off.
Some fans shown in the videos appeared to get past the fences and towards the venue. However, Wembley officials and police had earlier insisted there was no breach of stadium security and no ticketless fans had entered the actual ground.
The mood outside Wembley and in central London grew increasingly febrile well before the 1900 GMT kick-off as thousands of fans gathered on Olympic Way.
Some drunken fans were throwing beer cans and bottles as well as traffic cones, with red flares and fireworks set off.
Social distancing was ignored as maskless supporters congregated in large groups on the concrete approach to the stadium.
Meanwhile in Trafalgar Square in the city centre, a group of England fans tried to storm into a fan zone for 1,500 supporters who had won tickets in an online ballot.
Police said they were on-site to defuse the situation.
England has been gripped by Euro fever since Gareth Southgate's side booked the country's first major final appearance for 55 years.
The Three Lions are aiming to win a first trophy since the 1966 World Cup.
With coronavirus restrictions still in place, the final capacity at Wembley has been limited to 67,500, with around 7,500 seats reserved for Italy fans.
