The KNVB is shocked that a number of matches have been marred by incidents from the stands in recent times.

The football association calls the behavior of the fans involved completely unacceptable, according to a joint statement from the KNVB, Eredivisie CV and Keuken Kampioen Division on Thursday.

On Saturday, the Eredivisie game between FC Utrecht and RKC Waalwijk was temporarily suspended after beer and lighters were thrown on the field.

On Wednesday, things got out of hand again at FC Groningen-Vitesse when Vitesse goalkeeper Markus Schubert was hit by a cup of beer from the audience.

The KNVB and other parties involved speak of a worrying trend.

"In recent rounds, we increasingly see beer and objects being thrown on the field and visitors entering the field. We strongly disapprove of that and clear rules are being violated."

It is emphasized that throwing objects can create unsafe situations.

"We don't take any risk with regard to the safety of the players on the field. For that reason alone, it is completely unacceptable to throw beer or objects at players or enter the field."

'Disruptions are also increasing outside the Netherlands'

The increase in irregularities in the Eredivisie does not appear to be an isolated incident.

It also went wrong in several matches in France.

The derby between OGC Nice and Olympique Marseille was even permanently halted when fans clashed with players.

"The disturbances also seem to be increasing outside the Netherlands now that after the corona crisis, plenty of supporters are allowed to enter the stadium again. Of course we are concerned about this. The frequent suspension of matches and the handing out of penalties do not make football more fun", so says the statement.

Because 100 percent of the capacity can be used in football stadiums again from next weekend, the KNVB makes an urgent appeal to supporters: "We call on everyone to jointly support their club in a positive way."

If you don't, don't count on leniency.

"Clubs and KNVB are doing everything they can to track down perpetrators of disturbances. They can face a fine and a nationwide stadium ban for years."