Paris: The man who drove a truck into a crowd of people celebrating Bastille Day in the southern French city of Nice had researched the route days before the Thursday night attack, the media reported. The terrorist, identified as Mohamed Lahouaiej-Bouhlel, drove through the seafront Promenade area of Nice on Tuesday and Wednesday in preparation of the attack that left 84 people dead, BBC reported. Over 200 people -- 52 critically -- were also injured when the Tunisian man ploughed his heavy duty white truck into people enjoying the fireworks and music. The man opened fire at the crowd before he was shot dead by the police. As many as six people were later held in connection with the killings. The latest, a man and a woman who have not been identified, were arrested on Sunday morning, French judicial sources said. CCTV footage from the days beforehand showed the terrorist driving through the area in the truck, closely observing the scene. France has called up 12,000 police reservists to boost security in the wake of the killings which was the second major terror attack in the country after the November 2015 attacks in Paris that left 130 people dead and over 250 injured. BBC reported that the beaches and cafes in Nice were busy again and the Promenade was reopened on Saturday. People paid tributes and their respects to those, including 10 children, who were killed. The bloodstains on the tarmac are gradually disappearing. The lampposts the truck smashed into will be replaced. "He will never defeat us," said one message on Promenade. Another read: "Love defeats hate." Lahouaiej-Bouhlel's estranged wife, who was detained on Friday, was released on Sunday. Those still being held were said to be close associates of the killer but have not been identified. French President Francois Hollande, who has called the attack "terrorism", on Friday extended the state of Emergency in the country for three months beyond July 26. Officials said investigators will seek to find out whether the Tunisian had links with extremist groups. French Interior Minister Bernard Cazeneuve said Lahouaiej-Bouhlel seemed to have been "radicalised very quickly". He was unknown to French intelligence services although he had been in trouble with the police for threatening behaviour, violence and petty theft. It is not known if he trained in Syria or had any help planning the attack. The Islamic State militant group in a statement published in the Amaq news agency, said the attacker was acting in "response to its calls to target civilians in countries that are part of the anti-IS coalition".