“The person who carried out the operation in Nice, France, to run down people was one of the soldiers of Islamic State,” the news agency Amaq, which supports the militant Islamist group, said via its Telegram account.
“He carried out the operation in response to calls to target nationals of states that are part of the coalition fighting Islamic State,” the statement said.
French authorities and media have yet to produce any evidence that the killer, Mohamed Lahouaiej Bouhlel, was radicalized. The interior ministry said it was checking the claim.
The 31-year old Tunisian, who lived locally, drove at a Bastille Day crowd on the waterfront of the French Riviera city on Thursday night. Authorities had been working to find out what his motives were. He was not known to French intelligence sources for radicalization.
The arrests, which came on top of two others since the killing including the attacker’s wife, concerned his “close entourage”, police sources said. They were made in two different areas of Nice.
A Reuters reporter saw about 40 elite police raid a small apartment near the central station, where one individual was arrested.
The attack plunged France into new grief and fear just eight months after gunmen killed 130 people in Paris.
The truck zig-zagged along the seafront Promenade des Anglais for two kilometers as a fireworks display marking the French national day ended.
It was eventually stopped when police shot dead the driver.
The attack is the third of its kind in France since the beginning of 2015. A state of emergency in place since 130 people were killed in and around Paris last November is to be extended for another three months.
Bouhlel was known to police for petty crimes but was not on a watch list of suspected militants. He had one criminal conviction for road rage, having been sentenced to probation three months ago for throwing a wooden pallet at another driver.
Ahead of the claim by Islamic State, the militant Islamist group which grabbed control of swathes of Iraq and Syria but which is now under military pressure from forces opposed to it, French officials had not disclosed any direct evidence linking Bouhlel with jihadism.
Interior Minister Bernard Cazeneuve, asked on Friday if he could confirm the attacker’s motives were linked to jihadism, said: “No… We have an individual who was not known to intelligence services.”
Relatives and neighbors in Bouhlel’s hometown of Msaken outside the coast city of Sousse said he was sporty and had shown no sign of being radicalized, including when he last returned for the wedding of a sister four years ago.
Edwin Bakker, Professor at the Centre for Terrorism and Counterterrorism at the University of Leiden in the Netherlands, said the claim did not necessarily point to any formal link.
“Islamic State called for such (individual) attacks to be carried out back in 2014. They are also using the public perception that an attack like this seems to fit Islamic State. Investigators still have not discovered a direct link between Islamic State and the attacker, so it is a cheap claim,” he said.
In Nice, where the holiday season would normally be in full swing, organizers of the annual Jazz festival joined the singer Rihanna in cancelling their event. A five-day annual festival that has run since 1948 had been due to start on Saturday.
NISSA MA BELLE
Tearful well-wishers were still laying flowers, candles, teddy bears and drawings at a makeshift memorial on the Promenade des Anglais.
“Nothing will ever be like before…Nissa ma belle” read one, a reference to the hymn ‘Nissa la Bella’, or Nice the Beautiful, sung in the local Nicois dialect.
“Enough of the carnage. Stop the massacre,” read another.
Tora Hakausson, from Norway owns a flat in Nice, and was dining in a beach restaurant when the attack took place.
“We don’t want to go home. Life has to remain normal. I don’t want this to change how we feel about France,” she said as she wiped away a tear from under her sunglasses.
“Anger is the main emotion today,” said Maiche Arlette, a resident of the city. “For two and a half years now we have suffered from these attacks…”Our society has gone mad.”