Watch: AZ Alkmaar fans clash with police, opposition after West Ham loss

Supporters of Dutch club AZ Alkmaar clashed with riot police and opposition fans late Thursday after losing 0-1 to West Ham United in a Europa Conference League semi-final duel, news and social media reports said.

The incident is the latest in a series of escalating incidents of football violence in the Netherlands, which has worried both sports officials and politicians alike. 

AZ fans stormed the main stand at the AFAS stadium in the northwest Dutch city shortly after the final whistle, before brawling with West Ham supporters celebrating the win, the ANP national news agency said.

“The fans sat behind the AZ goal and broke through a gate to the main stand, after which they stormed celebrating West Ham fans,” the ANP said.

“From there, fists were flying,” it added.

Several players from both teams were also pulled into the fracas including West Ham United captain Declan Rice, reports said.

Footage posted Twitter showed a group of supporters, believed to be from AZ, breaking down a gate before seeking confrontation with West Ham United fans.

Other footage showed West Ham United players jumping over the boarding to intervene in the scuffle while frantically waving at people in the crowd.

In yet another clip, several police officers in riot gear drive back AZ supporters before restoring order to the stadium.

Whistles condemning the fans’ behaviour could also be heard from other AZ supporters in the stands.

West Ham United manager David Moyes after the match said his players had become involved because they wanted to protect friends and family.

“My relatives and friends were also on the stand. I only later saw what happened,” Moyes told the ANP news agency.

The incident is the latest in an escalation in football violence in the Netherlands.

On Sunday a referee halted a top division match between FC Groningen and Ajax after a Groning fan ran onto the field with a banner and smoke bombs were tossed on the pitch.

In another incident, Ajax midfielder Davy Klaassen received a head injury last month after a Feyenoord fan tossed a cigarette lighter at him from the stands.