Reports published in the name of two Islamic State media outlets said that the perpetrator was one of the group's "soldiers," although they did not mention whether there had been any prior coordination with the group.
The claims were published on social media channels in the name of Islamic State's Aamaq news agency and in an online audio file of the daily news bulletin from the group's al-Bayan radio.
While the authenticity of the postings could not be independetly verified, they were in line with previous claims by the group and were widely republished by its supporters.
The perpetrator was acting in response to the group's call for attacks on citizens of countries taking part in an international coalition fighting Islamic State in its Iraqi and Syrian territories, the statements said.
That, along with the fact that the statements did not suggest the attacker had acted on direct orders, seemed to point to the incident being a so-called "lone wolf" attack.
Islamic State has repeatedly called on its supporters to attack civilian targets in coalition member states using whatever means are available to them.
Analysts say Islamic State is happy to claim such attackers as members, even if they had no prior contact with it, as long as they have stated that they pledge their allegiance to Islamic State leader Abu Bakr al-Baghdadi.
On Thursday a 31-year-old man, identified as Tunisian national Mohamed Lahouaiej Bouhlel, was killed by police after driving a delivery truck for 2 kilometres through crowds of people along Nice's main promenade as a fireworks display to celebrate Bastille Day was coming to an end.
Sixteen of the victims' bodies still need to be identified, AFP reported Saturday, citing a hospital spokesman.
Also on Saturday, French President Francois Hollande met with his security cabinet to discuss defence measures, French new agency AFP reported.
Prime Minister Manuel Valls attended the meeting, as did Justice Minister Jean-Jacques Urvoas, Foreign Minister Jean-Marc Ayrault, Defence Minister Jean-Yves Le Drian, Interior Minister Bernard Cazeneuve and French army chief Pierre de Villiers.
Investigators are still working to establish a motive for attack and have not yet confirmed whether the perpetrator had contacts with radicalized Islamists.
AFP reported that authorities have arrested four people close to Bouhlel. His ex-wife has been in custody since Friday, according to the report.
On Friday Valls linked the attack to religious extremism.
"This is a terrorist who without doubt in one way or another was linked with radical Islamism," Valls told broadcaster France 2 on Friday.
But Bouhlel was "entirely unknown" to French intelligence authorities and wasn't on any of their lists of at-risk individuals, French prosecutors said.
Bouhlel's father insisted in comments made to AFP that his son was not religious: "He didn't pray, he drank alcohol and even took drugs."
He told AFP that his son had been treated for depression in his youth.
"Sometimes he had nervous breakdowns and broke and demolished everything," his father was quoted by the agency as saying.
In March he was sentenced to six months of probation for throwing a wooden pallet on a person after a car accident.
Since 2010 Bouhlel also had a history of threatening behaviour, theft, property damage and violence towards his wife, but was never incarcerated. He was no longer on the radar of the authorities at the time of the attack, the Justice Ministry said.
The Nice killings were the third major attack on French soil in 19 months, following shootings at the office of satirical magazine Charlie Hebdo and a Jewish supermarket in January 2015, and coordinated attacks around Paris last November.
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