Within weeks, Arkan had unified the various groupings of Red Star fans and turned them into a kind of paramilitary unit. These so-called 'fans' committed atrocities in Croatia and Bosnia during the first half of the 1990s, operating under the control of the Serbian security services.

After the wars in Bosnia and Croatia, the hooligans took part in rallies against Milosevic and contributed to his fall. But they did not confront the president because they had dreams of a European, democratic and liberal Serbia; they opposed him because he had lost the war.

Soon after the fall of Milosevic in 2000 and a few days into the new democratic Serbia, the country's most important football game – the Belgrade derby between Red Star and Partizan – had to be interrupted to stop furious fighting between hooligans from both sides on the pitch of the Red Star stadium.

The ensuing decade bred two different sides to a generation that no longer remembered Tito's post-war Yugoslavia. One side was raised in 1990s wartime misery and was frustrated by the slow improvement of living conditions afterwards. The other was brought up by well-to-do parents close to the Milosevic regime. Many lived in the West and learned foreign languages but they brought back to their home country the worst aspects of Western lifestyle.

Both sides are united by a hatred of Western, particularly American, ways and contempt for their regional neighbours, especially Albanians, Bosniaks and Croats. Elements from the secret services, nationalist political parties and even the ruling coalition thrive in this environment, but leaders of the most violent groups are often outright criminals involved in drug and weapon trafficking, as well as organised prostitution.

These groups have achieved a high level of impunity. Serbian governments follow a cautious approach, and the most popular football and basketball clubs are in their hands.

On several occasions, Red Star 'fans' have invaded their team's dressing room and hit the players. Players' cars were broken into and a torch was once rammed into a policeman's mouth. Partisan supporters in Belgrade killed a fan of the visiting French team Toulouse.

In 2008, hooligans of all stripes attacked and damaged the embassies of America, Germany and several other countries in Belgrade, while police looked on without intervening for several hours.

The police and the judiciary have only begun a few investigations into these cases, which have led to even fewer trials and verdicts. Journalists in Serbia seldom dare write openly about hooliganism surrounding football or basketball, knowing that they cannot rely on state protection for themselves and their families.

Exactly what the motives of those behind the most recent incidents in Belgrade and now in Genoa are is not clear. One school of thought is that the hooligans are controlled by secret service circles close to the ultra-nationalist camp intent on overturning the pro-European government.

Others believe the government itself is happy to let the hooligans run loose to demonstrate that President Boris Tadic's warning of ultra-nationalists taking control in Belgrade if the EU does not speed up accession talks with Serbia is real and should be taken seriously.

"It is quite interesting that the incidents in Genoa happened while US secretary of state Hillary Clinton was on an official visit in Serbia", said one EU diplomat.

"It is very strange that nobody from a nationalist organisation and no hooligan protested against the wife of the man [ex-president Bill Clinton] who decided to bomb Serbs twice; in Bosnia in 1995 and in Serbia in 1999. Wouldn't it be better for the Serbian government to have the hooligans far way from Belgrade while Mrs Clinton was in town?"