Police investigate whether Nice massacre was linked to terror group

French police are trying to establish whether the Tunisian who killed at least 84 people by ramming a lorry into Bastille Day crowds in Nice acted alone or belonged to a network that had eluded the intelligence services.

The driver, 31-year-old Mohamed Lahouaiej Bouhlel, had one conviction for a road rage incident that occurred three months ago, but prosecutor François Molins said he was "completely unknown" to the intelligence services.

The lorry careered into crowds of people on the Promenade des Anglais as a fireworks display marking the French national day ended on Thursday night. It zig-zagged along the seafront for almost 2km before Bouhlel was shot dead by police. Of the scores of injured, 25 were on life support on Friday.

Mr Molins said the authorities would try to determine whether the attacker had accomplices. “It will also try to find out whether Mohamed Laouaiej Bouhlel had ties to Islamist terrorist organisations,” he told a press conference in Nice. Although the attack has not been claimed by any outfit, “this sort of thing fits in perfectly with calls for murder from such terrorist organisations,” Mr Molins said.

Senior government figures took the same line, with prime minister Manuel Valls saying the driver was "a terrorist probably linked to radical Islam one way or another."

Bouhlel, a heavy-goods vehicle driver, reportedly rented the 19-tonne refrigerated lorry in the days leading up to the attack. When police examined the vehicle after the attack, they found a bicycle, an automatic pistol, two fake assault rifles, a nonfunctioning grenade, a mobile phone and some papers. Bouhlel’s ex-wife was later taken into police custody, the prosecutor said.

Police carried out a controlled explosion on a white van near Bouhlel's home, in a residential neighbourhood in northern Nice. The explosion blew the doors open and shattered glass, but it was not clear whether they found anything incriminating. Bouhlel was legally resident in France, having left his Tunisian home town Msaken, near the coastal city of Sousse, a number of years ago.

France has responded to the massacre by extending by a further three months a state of emergency that was imposed after multiple coordinated attacks in Paris last November. Military and police reservists are to be called up to help enforce it.

In a televised address, President François Hollande said France was "filled with sadness by this new tragedy" and said the government would "further strengthen" its actions against Islamic State in Iraq and Syria. "We are facing a battle that will be long because facing us is an enemy that wants to continue to strike all people and all countries that have values like ours," he said.

With presidential and parliamentary elections just a year away, the latest atrocity was seized on by Mr Hollande's opponents as proof of wider security failings at home. Christian Estrosi, a security hardliner and mayor of Nice until last month, said he had written to Mr Hollande on the eve of the attack to demand more funding for police.

“As far as I’m concerned, I demand answers, and not the usual stuff,” Mr Estrosi said on BFM TV, asking whether the government provided enough national police officers for the fireworks display. Mr Valls later said security for the display was at the same level as for Euro 2016 events, where the police presence was greater than usual due to fears of terrorist attacks.

If police find a link between Bouhlel and jihadi networks in France, it will raise further difficult questions for the authorities in a city where dozens of would-be jihadis have been recruited.

The French administrative department of Alpes-Maritimes, of which Nice is the capital, said at the end of last year that 236 individuals had been monitored over several months as part of a surveillance programme and that it was tracking five new individuals every week. The region of just over a million people is thought to be home to 10 per cent of all of French citizens gone abroad to join radical Islamist groups.