The president of Serbia's Football Association was on Sunday questioned by police in connection with recent arrests of several members of football fan groups accused of murder, kidnapping and drug trafficking.

Serbian media said Slavisa Kokeza was quizzed over his links to leaders of Partizan Belgrade supporter groups who were arrested earlier this month in what officials say is a major crackdown against football's links with organized crime.

Details from the police investigation leaked to the media include alleged killings by group members of their rivals, including decapitations and torture in a special "bunker" at the Partizan stadium in the Serbian capital.

Populist Serbian President Aleksandar Vucic, who has often boasted about his youth as a radical supporter of Partizan’s rival Red Star Belgrade, said Saturday that some of the "shocking" details of the investigation will be made public next week and that children will be warned not to watch.

Serbia has a history of tolerating hooliganism that often resulted in violence and outbursts of nationalism at stadiums. During the Balkan wars in the 1990s, many of them joined notorious paramilitary groups linked to war crimes against other national groups in the former Yugoslavia.

Earlier last week, European football's governing body UEFA opened a disciplinary investigation after AC Milan's Zlatan Ibrahimovic was subjected to racist abuse in a Europa League match against Red Star Belgrade.

With the return of nationalists to power in Serbia nine years ago, far-right football supporters were often seen at pro-government rallies promoting a nationalist political agenda. In exchange, analysts say, the hooligans have been allowed to pursue their illegal business activities.

More than a dozen prominent figures from the country’s football supporters’ groups have been murdered in recent years. Most have perished in gangland-style killings.