French police on Sunday arrested a man and a woman with ties to the man behind a truck ramming attack claimed by the Islamic State (Daish) group, a judicial source said.

AFP reported, five other people are already in custody, including the estranged wife of Mohamed Lahouaiej-Bouhlel, a Tunisian with no apparent links to extremism who is said to have been radicalised very quickly.

Lahouaiej-Bouhlel was shot dead by police after he rammed a truck through a crowd celebrating France's Bastille Day in the resort city of Nice, leaving 84 dead and about 300 more injured.

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