Kenzo Tribouillard, AFP file picture | The attacker killed four people in the kosher supermarket before police stormed him and shot him dead

Ten people, including a suspected arms dealer, are in custody as part of an investigation into a deadly 2015 attack on a Jewish supermarket in Paris, sources close to the probe said Wednesday.

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Claude Hermant, who is awaiting trial in a separate arms trafficking case, and the other suspects have been rounded up since Monday, and there could be more arrests, the sources said.

Investigators are trying to piece together how France-based jihadist Amedy Coulibaly obtained the weapons used in the January 9, 2015 attack.

Coulibaly killed four people after taking shoppers hostage at the Jewish store. Elite police later shot him dead as they stormed the building.

He had killed a policewoman in the Montrouge suburb south of Paris the night before, when authorities think he may have initially been targeting a nearby Jewish school.

The attack was part of three days of terror in the French capital that began with the raid on the Charlie Hebdo satirical magazine offices that killed 12 people.

So far investigators know the weapons came from Slovakia and were made inoperable, then handled by a middleman in Belgium before being resold to the company of Hermant's girlfriend.

Hermant, who prosecutors say has links with far-right groups in northern France, and his girlfriend were questioned in December 2015 over the supermarket attack without being charged.

During questioning, Hermant denied remilitarising the weapons or any knowledge of an attack plot.

(AFP)

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