The use of a 19-ton truck to cut down scores of seaside revelers in Nice, France — if connected to jihadist-inspired terrorism — would represent a dramatic escalation in what experts describe as an emerging trend in attacks: simple, even crude instruments employed to kill ever-larger numbers of people.

Thursday’s rampage appears to have set a grisly new standard as one of the deadliest attacks in years in which most victims were killed by nonexplosive means. ­Instead of guns or bombs, the driver mainly used his vehicle to crush men, women and children who had gathered to watch a fireworks display.

Investigators are still looking for clues that the driver, identified on Friday as a Tunisian-born immigrant with a record of petty crime, had any ties to extremists. But intelligence officials and terrorism experts worried that the attack’s stunning effectiveness could serve as an inspiration to terrorist groups around the world, while perhaps portending yet another evolution in the methodology used by violent jihadists loyal to al-Qaeda or the Islamic State.

“We have reached a stage where terrorist organizations want to create an environment in which they could hit anywhere at any time, using whatever method,” said a European security official, who spoke on the condition of anonymity to discuss sensitive assessments of terrorist strategy. “The videos and messages against France and other European countries have been published in various social-media platforms, with the message to ‘use whatever to kill, even cars.’ ”

Since June, suspected terrorists have launched five major attacks on three continents, all using comparatively simple but lethal technologies, from small arms to simple explosives. U.S. officials have issued repeated warnings that even cruder tactics, such as vehicle assaults on crowds, could happen in the United States. A 2010 Department of Homeland Security report said overseas terrorists were contemplating “vehicle ramming attacks — using modified or unmodified vehicles — against crowds, buildings” and other targets likely to feature large concentrations of people. Such attacks could be carried out by individuals with “minimal prior training or experience,” the report warned.

[Tunisian immigrant suspected in French terrorist attack]

“The use of a large truck in the attack — alongside the high death toll and deliberate targeting of a large crowd at an ideologically symbolic event — represents an evolution in the use of the tactic and potentially indicates a higher level of operational planning,” said Matthew Henman, who heads the Terrorism and Insurgency Center at IHS Jane’s, a private firm specializing in military and security analysis. Henman warned of a heightened risk of “copycat attacks” in France and elsewhere in the near future.

The assault along one of the French Riviera’s most renowned promenades follows a series of calls by both the Islamic State and al-Qaeda affiliates for spontaneous acts of terror by any means available. Abu Muhammad ­al-Adnani, the chief spokesman for the Islamic State, specifically encouraged using automobiles as weapons.

“If you are not able to find an IED [improvised explosive device] or a bullet, then single out the disbelieving American, Frenchman, or any of their allies. Smash his head with a rock, or slaughter him with a knife, or run him over with your car, or throw him down from a high place, or choke him,” Adnani said in a 2014 message. Such appeals have increased in recent months as the military offensive against Islamic State strongholds gains momentum.

In recent weeks, scores of civilians have been slaughtered by jihadist-inspired assailants using mostly small arms, blades and grenades, from the June 12 shooting rampage in the Pulse nightclub in Orlando to the June 29 assault on Turkey’s Ataturk International Airport to this month’s terrorist attack in Dhaka, Bangladesh, by militants armed with pistols and machetes. Even the Islamic State’s trademark suicide bombings rely on a relatively simple design, including an explosive that can be assembled from commonly available ingredients.

[Witnesses describe gruesome scene as truck slammed into revelers]

Other Islamic State-inspired attacks have involved the use of automobiles as weapons, though never with such deadly results. Assault-by-vehicle attacks in two French cities in 2014 killed one person and wounded 20, and a similar incident in January wounded a French soldier in the city of Valence. Islamist attackers in London killed an off-duty British soldier by striking him with a car and then stabbing him.

French investigators have so far identified only a single perpetrator — the driver, Mohamed Lahouaiej Bouhlel, a Tunisian-born Frenchman — in Thursday’s attack, but analysts say the high death toll suggests careful planning to ensure maximum carnage.

“The fact that the driver had guns and grenades with him suggests that this is more complicated than someone getting in a truck and deciding to plow into a crowd on a national holiday,” said Bruce Hoffman, a professor and director of the Security Studies Program at Georgetown University.

Thursday’s event occurred a week after the end of the Muslim holy month of Ramadan, which the Islamic State’s leaders had designated as a time for accelerated terrorist attacks around the world. To some analysts, it suggests that the heightened tempo of assaults over the past month was not a temporary aberration.

“The West was initially in denial of the magnitude of the threat, believing it could be contained to the perennially violent Levant and Iraq,” Hoffman said. “Then we imagined that counter-radicalization programs and ramped-up intelligence could manage the threat in our own countries.

“The events of the past eight months — and especially the past weeks — are exposing that as wishful thinking,” he said.

Mekhennet reported from Frankfurt, Germany.

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