The Islamic State group claimed responsibility for the truck attack that killed 84 people in Nice on France's national holiday, the jihadist organisation said Saturday in its official radio bulletin.
The statement from Al-Bayan said an ISIS "soldier" carried out a "new, special operation using a truck" to cause Thursday's carnage.
Mohamed Lahouaiej-Bouhlel, 31, rammed a 19-ton truck into a large crowd as July 14 fireworks were ending in the French Riviera city.
At least 10 children were among the dead and 50 more were wounded, some of them critically, a hospital official said.
Al-Bayan warned that Western countries "will not be spared from the blows of the mujahideen," no matter how much they increase their security measures.
Earlier, a social media account linked to the ISIS-affiliated Amaq news service quoted a security source as saying the attack was "in response to calls to target nations of coalition states that are fighting Islamic State."
The jihadist group has called on its supporters living in Europe to carry out lone-wolf attacks on Westerners, publishing a video early this year called "Kill wherever you find them."
French President Francois Hollande said in the wake of the Nice attack that France would strengthen its role in Iraq and Syria, where it is part of a US-led coalition fighting the jihadists.
Prime Minister Manuel Valls said the attacker probably had links to radical Islam, but Interior Minister Bernard Cazeneuve cautioned it was too early to make the connection.
The terror group also claimed responsibility for the November 13 attacks in Paris which killed 130 people.