Details are emerging about the shadowy figure of Claude Hermant, a former member of a paramilitary organisation within Front National (FN) who has been arrested in Lille on suspicion of providing weapons to gunman Amedy Coulibaly for his deadly attack on a kosher supermarket in Paris in January.

Several of the weapons used by Coulibaly were traced back to a company managed by Hermant, who was already in jail on illegal arms trade charges.

A former paratrooper and boxing champion, the 52-year-old claims he was an informant for gendarmes and customs police who might have "squandered a big fish at risk of fuelling the Paris' arms trade", according to La Voix du Nord newspaper, who published an email exchange with a policeman.

In the late 1990s, Hermant was a member of a secret military group – DPS, or Département Protéction et Sécurité – that was part of the far-right FN party, now led by Marine Le Pen, whose mission was to provide security for senior party members. In a 2001 article in French publication Liberation, Hermant was quoted while describing his activities within a DPS subgroup he called "the Ghosts" or "group the shock", which included 200 former military personnel.

Infiltrating anti-FN organisations – namely anti-hate, anti-racists groups – and carrying punitive expeditions in the banlieues against youth gangs with the aim of fuelling unrest and boosting support for the far-right party were among the group's activities listed by Hermant.

He had also been one of the leaders of the Maison du Peuple Flamand, an-ultra nationalist group in the Lille area.

His adventurous life led him to the Republic of Congo, where he underwent a botched mercenary mission that resulted in him being jailed for seven months. That is when he fell out with FN, as only a pardon by president Denis Sassou N'Guesso got him out of prison.

That is also why he went to Liberation discuss the party's secret security service in 2001. The FN denied the existence of the Ghosts but Hermant made headlines as an infamous figure of the extreme right in northern France. He has been linked to Bloc Identitaire, a far-right organisation rejected by Marine Le Pen.

Investigators suspect Coulibaly, who was killed during the police assault on the Hypercacher supermarket in eastern Paris, purchased the weapons from an arms dealer in the Belgian city of Charleroi who has been linked to Hermant. The weapons, an assault rifle and four Tokarev guns, were alleged to have been illegally reconverted by Hermant's company.