Three men have reportedly been charged with supplying the weapon used by Cherif Chekatt in the Christmas market attack that killed five people and wounded 11 in the French city of Strasbourg.

The three suspects, from the same family and aged 32, 34 and 78, were indicted and placed in custody by an examining magistrate in Paris for “possession and transfer of a category B weapon in relation to a criminal terrorist enterprise” and for “conspiracy with terrorist criminals”, according to a judicial source.

The three men were arrested on Tuesday in eastern France. They are alleged to have supplied an 8mm pistol used by Chekatt in the 11 December attack. Two other members of the same family were detained and later released without charge. On 17 December another man, a relative of the killer, was arrested and charged on the same counts.

Chekatt, 29, who had been on a special watchlist as a suspected radical Islamist, was shot dead by police after a two-day manhunt in the city on the German border. Anti-terrorist police believe Chekatt obtained the firearm a few days before the attack.

Judicial sources said Chekatt had pledged allegiance to the Islamic State group in a video found on a USB key. The interior minister has dismissed a claim by the Islamic State group that it was responsible for the attack.

France has been on high alert since the start of a wave of jihadist attacks in 2015 which have killed 251 people.