Dutch government to investigate Feyenoord and Ajax violence
The game was stopped for almost 30 minutes after Ajax midfielder Davy Klaassen suffered a head wound, and there was also crowd trouble with fireworks and anti-semitic chants.
Dutch Justice Minister Dylan Yesilgoz said the incident would be investigated "at the highest level."
She and Sports Minister Conny Helder will hold talks with the Dutch Football Federation, clubs, municipalities and the police to find out what happened.
"If you continue like this, you will get a situation where even home supporters will be banned,” Yesilgoz told the ANP news agency.
Games between the bitter Amsterdam and Rotterdam rivals are often flashpoints but there has been a rising incidence of football violence in the Netherlands.
Fifa President Gianni Infantino urged Dutch authorities to take action.
"There is absolutely no place for violence in football, on or off the field," Infantino said on his Instagram account.
"Such events... have no place in our sport or in society all players have to be safe and secure to play the game, and I call on the relevant authorities to ensure that this is respected at all levels."
The Dutch Football Federation KNVB also condemned the incident.
"Dutch football has sunk to a new low”, the KNVB said in a statement.
"Thousands of people go to the stadium to watch the players play football. Then it is insane that they are apparently not safe on the field."
Referee Allard Lindhout stopped the game in the 63rd minute for almost half an hour after a lighter thrown from the stands hit Klaassen, who was left with a bleeding head wound.
Ajax eventually won 2-1 to qualify for the final where they will play PSV Eindhoven.
Klaassen, who scored his team's second goal in the 51st minute, tried to continue after the restart but left the pitch a few minutes afterwards, holding his head.
Dutch newspapers called for action.
"How long will this still go on?” asked the daily tabloid De Telegraaf in a headline.
"Yet again something went wrong at this classic match, where away supporters are in any case not allowed," the paper said.
The Dutch police union told the Algemeen Dagblad tabloid that the referee should have stopped the match altogether.
"Such bad behaviour should not be rewarded," the union said.
