Paris: A French judicial official says the alleged gunman who shot and killed five people in a Christmas market attack this month in Strasbourg had pledged allegiance to the Islamic State group.

The judicial official, who is not authorised to speak publicly about the investigation, said investigators have found a video stored on a USB key in which Cherif Chekatt had claimed allegiance to the extremist group. The video was at Chekatt's home.

Chekatt, 29, died in a shootout with police two days after his December 11 attack at Strasbourg's popular Christmas market.

Shortly after his death, the Islamic State group's Amaq news agency claimed he was a "soldier" of the group. French Interior Minister Christophe Castaner had rejected the claim as "totally opportunistic."

AP