A brawl ensued after home fans broke through a fence and attacked visitors sitting in a reserved section following the Europa Conference League semi-final on Thursday night.

In a statement on Friday morning, Netherlands Police said no arrests have yet been made but they are reviewing footage from the stadium and trying to identify the culprits.

"Arrests may follow this," the force warned.

"Together with AZ, the municipality of Alkmaar and the public prosecution service we will evaluate last night's incidents, which we regret having happened. This kind of behaviour has no place in football," the statement added.

UEFA, European football's governing body, is also expected to launch its own probe after the incident was captured widely on video.

It unfolded after the final whistle at the AFAS Stadion, which saw West Ham reach their first major European final since 1976 after a 1-0 second-leg win (3-1 on aggregate).

AZ Alkmaar supporters dressed in black with their faces covered managed to get into the area where West Ham's friends and family were seated.

After the violence broke out, several West Ham players, including captain and England international Declan Rice, tried to intervene.

West Ham's Michail Antonio, Said Benrahma, Aaron Cresswell and Flynn Downes were also seen climbing over advertising boards in a bid to protect their loved ones.

Stewards and police arrived as spectators looked on and calm was restored 10 minutes later.

'Was I worried? Yeah, my family were there'

West Ham manager David Moyes, whose 85-year-old father was in the targeted section of the stadium, said afterwards: "I can only say the players were involved because it was the family section and most of their family and friends were in there.

"That was probably the reason for the reaction.

"Was I worried? Yeah, my family were there and I had friends in that section. You're hoping they would try and get themselves away from it.

"I didn't recognise it because I'd gone onto the pitch. Security wanted to take me inside, but I had to make sure my players weren't involved."

Sky Sports reporter Gary Cotterill sat close to where the "chaos" unfolded.

He said it took "some time" for officials to intervene.

"Police moved in, in riot gear as well, and by then it really was chaos. You can understand the anxiousness and the concern of the West Ham players," he added.

After their semi-final win, West Ham will face Italian side Fiorentina in the UEFA Europa Conference League final in Prague on 7 June.