PARIS — For years they operated in the shadows, but militant extreme-right groups have become increasingly visible in France.

Since the death of a university student this week in a melee between skinheads and militant leftists, the French government says it wants to ban extreme-right groups – a complex task complicated by the hydra-like nature of the hard-core right.

Five people linked to extreme-right groups were still being questioned Friday in the student's death in Paris, according to the prosecutor's office. Eight had been initially held.

An autopsy was being done Friday on the body of 19-year-old Clement Meric, a student at Sciences Po, one of France's most prestigious universities. He died in the hospital after the clash Wednesday.

Investigators are trying to establish whether the suspect who reportedly delivered the deadly blow belongs to the Revolutionary Nationalist Youth, a far-right group led by long-time extremist Serge Ayoub, or another extreme-right movement.

Ayoub – a former skinhead nicknamed "Batskin" – denied on BFM-TV that those in the clash were part of his organization but conceded they quickly contacted him for advice after the brawl.

"They're panicking. Of course they regret it," he said.

French television later showed him emerging from a police station, reporting he had been questioned as a witness in the case because of the alleged ties to his group among some of those held.

What triggered the confrontation remains unclear. But the student's death spurred an outpouring of indignation, finger-pointing among politicians and calls for authorities to ban extreme-right groups.

Extreme-right groups have gained attention in numerous European countries, particularly Greece, where the Golden Dawn party, broadly vilified for alleged Nazi sympathies and violence against immigrants, holds seats in parliament.

France's rejuvenated far-right party, the National Front, has been excluding jack-booted extremists from its ranks but worries about a rise in independent movements.

The government "will do everything to dissolve these groups," Interior Minister Manuel Valls said, adding it "takes time" to establish the facts and show cause.

An expert on the extreme right, Nicolas Lebourg of the University of Perpignan, said the structure of groups complicates the situation.

"Movements are subdivided into several movements. That helps avoid dissolution by the government," he said by telephone.

Ayoub, for instance, heads the Revolutionary Nationalist Youth group, which is linked to his other movement, the Third Way. He also heads another spinoff, the Popular Solidarity Front, which supports militant worker action, and even did some politicking before last year's presidential race.

The extreme right – to the right of the National Front party – was a powerful force in France, veritable armed militias, in the 1930s. "Groupuscules," or tiny groups, of extreme rightists were known for violence two decades ago. Then they all but disappeared from the French landscape until the National Front party began a purge of extremists as part of its progressive image change under its new leader, Marine Le Pen, to become more palatable to voters.

"The National Front once welcomed everyone," Lebourg said. But in trying to normalize, the party pushed out the jackboot-clad radicals. Extreme-right "groupuscules" increased and "hardened," he said.

In recent months, extreme-right groups became a visible part of the massive French protests against gay marriage, which was legalized here in May.

Lebourg estimates there are some 3,000 extreme-rightists in France, a mixed bag of ideologies that include anarchists, anarchist-royalists and the non-violent Identity Bloc, a group opposed to Muslim immigrants and the European Union.

Ayoub actually serves a purpose among hotheaded extreme-rightist youth, Lebourg said.

He "talks very tough but he provides down-and-out youth with a framework," Lebourg said. "He always poses with a baseball bat ... but he doesn't practice that. It's theater, Hollywood with a little budget."

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  • Unidentified students react in front of the Institut d'etudes Politiques, also known as Sciences Po, Thursday, June 6, 2013. A group of skinheads attacked a French far-left activist in the heart of Paris' shopping district, leaving the young man brain-dead in the hospital Thursday, officials said, in an attack that raised fears of increased far-right violence. (AP Photo/Jacques Brinon)

  • Institute of Political Studies(IEP) or Sciences Po President Frederic Mion, right, welcomes Secretary General of France's Socialist Party, Harlem Desir, in front of the Institut d'etudes Politiques, Thursday, June 6, 2013. (AP Photo/Jacques Brinon)

  • Participants gather in front of the Institut d'etudes Politiques, also known as Sciences Po, Thursday, June 6, 2013. (AP Photo/Jacques Brinon)

  • Flowers sit at the site where left-wing activist Clement Meric was allegedly attacked by skinheads on June 6, 2013 in Paris, France. (Photo by Antoine Antoniol/Getty Images)

  • People walk past the site where left-wing activist Clement Meric was allegedly attacked by skinheads on June 6, 2013 in Paris, France. (Photo by Antoine Antoniol/Getty Images)

  • Flowers sit at the site where left-wing activist Clement Meric was allegedly attacked by skinheads on June 6, 2013 in Paris, France. (Photo by Antoine Antoniol/Getty Images)

  • Flowers sit at the site where left-wing activist Clement Meric was allegedly attacked by skinheads on June 6, 2013 in Paris, France. (Photo by Antoine Antoniol/Getty Images)

  • Flowers sit at the site where left-wing activist Clement Meric was allegedly attacked by skinheads on June 6, 2013 in Paris, France. (Photo by Antoine Antoniol/Getty Images)

  • Left-wing militants pay tribute to Clement Meric who was attacked by skinheads on June 6, 2013 in Paris, France. Meric was reportedly left brain dead after a fight with skinheads thought to be associated with a small far-right group. (Photo by Antoine Antoniol/Getty Images)

  • Left-wing militants pay tribute to Clement Meric who was attacked by skinheads on June 6, 2013 in Paris, France. Meric was reportedly left brain dead after a fight with skinheads thought to be associated with a small far-right group. (Photo by Antoine Antoniol/Getty Images)

  • Left-wing militants pay tribute to Clement Meric who was attacked by skinheads on June 6, 2013 in Paris, France. Meric was reportedly left brain dead after a fight with skinheads thought to be associated with a small far-right group. (Photo by Antoine Antoniol/Getty Images)

  • Demonstrators raise their fists on June 6, 2013 during a demonstration at Place Saint-Michel in central Paris, after a young far-left activist was killed during a fight with skinheads in central Paris. Clement Meric, an 18-year-old French far-left activist and student at the city's prestigious Sciences-Po university, died on June 6 following the fight, a police source said. Clement Meric had been left brain dead after the violence on June 5. The police source said three men and one woman had been held and that the attacker who is thought to have dealt the fatal blow denied having an intention to kill. (PIERRE ANDRIEU/AFP/Getty Images)

  • Demonstrators march through the streets of Nantes holding a banner reading, 'Neither forget, nor forgive, justice for Clement, anti-fascist riposte,' on June 6, 2013 after a young far-left activist was killed during a fight with skinheads in central Paris. Clement Meric, an 18-year-old French far-left activist and student at the city's prestigious Sciences-Po university, died on June 6 following the fight, a police source said. Clement Meric had been left brain dead after the violence on June 5. The police source said three men and one woman had been held and that the attacker who is thought to have dealt the fatal blow denied having an intention to kill. (FRANK PERRY/AFP/Getty Images)

  • Demonstrators wave flags as they gather on June 6, 2013 in the Vieux-Port of Marseille, southern France, after a young far-left activist was killed during a fight with skinheads in central Paris. Clement Meric, an 18-year-old French far-left activist and student at the city's prestigious Sciences-Po university, died on June 6 following the fight, a police source said. Clement Meric had been left brain dead after the violence on June 5. The police source said three men and one woman had been held and that the attacker who is thought to have dealt the fatal blow denied having an intention to kill. (GERARD JULIEN/AFP/Getty Images)

  • Demonstrators leave flowers near text reading 'Fascists get out of our lives !' as they gather on June 6, 2013, at the spot where a young far-left activist was killed after a fight with skinheads in central Paris, sending shockwaves through the French capital amid concern over the rise of small extreme-right groups. The country's interior minister Manuel Valls condemned the violence, which he said 'bears the marks of the far-right', noting that Clement Meric was 'hit extremely violently by several skinheads' in a fight on June 6, 2013. (JACQUES DEMARTHON/AFP/Getty Images)