European soccer fans are a different breed, so when the followers of Holland’s premier team, Ajax, began filling stadiums with songs that “We are the super-Jews,” most observers just rolled their eyes.

However, some were not amused. A group called BAN, which is an acronym for a group fighting antisemitism, has sued. Their complaint has been filed in Amsterdam District Court against the Ajax soccer club and the mayor of Amsterdam, Eberhard van der Laan, accusing them of racism.

BAN says that Ajax has no Jewish roots and few Jewish fans, and thus, no right to claim to be “super-Jews.”

Craig S. Smith for the New York Times attended an Ajax game a few years ago and was just as puzzled as most outsiders:

Outside, souvenir stalls sold Israeli flags or flags with the Ajax logo, the head of the fabled Greek warrior, emblazoned inside the star of David. Fans arrived with hats, jackets and scarves embroidered with Hebrew writing. Until recently, the team’s official Web site even featured the ringing tones of Hava Nagila and other Jewish songs that could be downloaded into fans’ mobile phones.

Yet, Smith marvelled: “Few, if any, of these people are Jewish.” So, why the chants, the flags, the songs?

“About thirty years ago, the other teams’ supporters started calling us Jews because there was a history of Jews in Ajax,” explained Fred Harris, a stocky man with brush-cut hair and a thick gold chain around his neck, “so we took it up as a point of pride and now it has become our identity.”

For years, the team’s management supported that unique identity. But over time what seemed to many people like a harmless —  if peculiar — custom has taken on a more sinister tone. Fans of Ajax’s biggest rivals began giving the Nazis’ signature straight-arm salute or chanting “Hamas, Hamas!” to provoke Ajax supporters. Ajax games have been marred by shouts of “Jews to the gas!” or simply hissing to simulate the sound of gas escaping.

During a game against a German team late last year, a group of Ajax supporters displayed a banner that read “Jews take revenge for ’40-’45,” a reference to the Holocaust.

There is no clear reason why Ajax, founded in 1900, became known as a Jewish club. Amsterdam has always had the largest Jewish population in the Netherlands and the club had two Jewish presidents in the 1960’s and 1970’s. It has had Jewish players at various times. The club, which owns 73 percent of the listed company that owns the team, also has some Jews among its 400 members, but no greater a percentage than their representation in the city’s general population. There are no Jews on the club’s current board.

However, BAN wants it to stop. Chants such as “We are the super-Jews” encourage racial hatred, according to the complaint.

In August, The Hague District Court ordered another soccer club, ADO Den Hague, to stop chanting, “Hamas, Hamas, Jews to the gas” at Ajax games. The judge rejected ADO’s claim that the chants were not antisemitic or directed in any way toward actual Jews.

The judged ordered referees to halt future games if such chants recur.

Both the Ajax soccer club and the mayor of Amsterdam pledged to stop the chants.

Because the tradition has continued, BAN is pursuing its suit.