Amedy Coulibaly, one of gunmen behind the worst militant attacks in France for decades, declares his allegiance in an unknown location to the Islamic State and urges French Muslims to follow his example, in this still image taken from video January 11, 2015. REUTERS/Social Media via Reuters TV

BRUSSELS (Reuters) - Belgian authorities have detained a man for arms dealing and are investigating whether he supplied one of the Islamist gunmen who together killed 17 people in Paris last week, prosecutors said on Thursday.

Belgian media reported that a man had handed himself in to police in the southern city of Charleroi on Tuesday, saying he had been in touch with Amedy Coulibaly, the militant who took hostages in a Jewish supermarket in the French capital and was later killed by security forces.

According to the reports, the man said that he swindled Coulibaly in a car sale, but police later found evidence that the two were negotiating about the sale of ammunition for a 7.62 mm caliber firearm.

Bullets of this caliber are needed for the Tokarev pistol that Coulibaly used in his attack on the supermarket in Paris, where he killed four hostages, and possibly in the shooting and injuring of a jogger two days earlier.

“The man is being held by the judge in Charleroi on suspicion of arms dealing,” a spokesman for Belgium’s federal prosecution said. “Further investigations will have to show whether there is a link with the events in Paris,” he added.