A van attack in Barcelona that left at least 13 dead and 80 injured is being investigated as a terror attack. The incident is the latest in a series of vehicle ramming attacks, coming less than a week after a man drove a Dodge Challenger into a crowd of people protesting against a white nationalist rally in Chalottesville, Va., killing a 32-year-old woman.

Extremists seem to be increasingly turning to vehicle ramming attacks in part because they are cheap, easy to organize and hard to prevent, experts say.  

The tactic of mowing people down with a vehicle eliminates the need for explosives or weapons and can be carried out by a "lone wolf" attacker without a network of fellow militants — all lessening the risk of alerting security agencies beforehand.

"This kind of attack doesn't need special preparation. It is very low cost, within anybody's reach," said Sebastien Pietrasanta, a French Socialist lawmaker and terrorism expert.

"It is often a case of individual action," he told Reuters. "They can be quite spontaneous."

Here's a look at some of the recent attacks where vehicles were used.  

Aug. 17, 2017: A white van was driven into pedestrians on Barcelona's busy Las Ramblas strip, an area in central Barcelona popular with tourists and locals and filled with cafés, bars, shops and restaurants early evening Thursday, killing at least 13 people and injuring dozens. Police have arrested two people in connection with the attack and have said they are investigating it as an act of terrorism. Maghrebi Driss Oukabir has been identified as the person who rented the van that was used in the attack. It is not known if he is one of the suspects in police custody. 

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Vehicle ramming is a method increasingly being used by extremists as a cheap, easy to organize and hard to prevent way of causing casualties, experts say. (Oriol Duran/Associated Press)

Aug. 12, 2017: A Charlottesville, Va., resident among hundreds of protesters who had gathered in that city to decry a large gathering of white nationalists when the driver of a Dodge Challenger barrelled toward them on a downtown street. Video from the scene showed the car reversing and hitting more people. One woman, Heather Heyer, 32, was killed. A 20-year-old Ohio man has been charged.

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A vehicle drives into a group of protesters demonstrating against a white nationalist rally in Charlottesville, Va., on Aug. 12. Heather Heyer, 32, was killed in the incident. (The Daily Progress via AP)

June 19, 2017: A man on the radar of French authorities was killed after ramming a car carrying explosives into a police vehicle on Paris's famed Champs-Elysée boulevard. No police officers or passersby were hurt. The attacker's motives were unclear, though officials said the action was apparently deliberate. 

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A masked French policeman secures the area on the Champs Elysees avenue after an incident in Paris, France, June 19, 2017 . (Gonzalo Fuentes/Reuters)

June 3, 2017: Seven people were killed and dozens more injured in a rampage that began when a van barrelled into pedestrians on London Bridge. Three men fled the van with large knives and attacked people at bars and restaurants in nearby Borough Market. Police declared the attacks "terrorist incidents" and said they had killed three attackers. 

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Five people were killed and 40 injured in an attack in London March 22, which started when a man plowed a vehicle into crowds outside Parliament.

April 7, 2017: A hijacked beer truck plowed into pedestrians at a central Stockholm department store, killing four people and wounding 15 others in what Sweden's prime minister called a terrorist attack.

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People react as police respond to violence in London on Saturday evening. (Hannah McKay/Reuters)

March 22, 2017: A man went on a deadly rampage in London, plowing a car into pedestrians on Westminster Bridge before stabbing a police officer to death inside the gates of Parliament. Five people were killed, as well as the assailant, Khalid Masood, and 40 others were injured.

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The rear of a truck, left, protrudes from a department store in central Stockholm, Sweden, on April 7, after plowing down the street killing four people and injuring 15. (Anders Wiklund/TT News Agency via AP)

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Jan. 20, 2017: A man with a history of mental health and drug abuse issues drove into a street crowded with pedestrians in Melbourne, Australia's second-largest city, killing four people, including a child, and injuring around 15 others. The 26-year-old man was arrested, and police said the incident had no links to terrorism.

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On March 22, a man drove a rental car into crowds on London's Westminster Bridge before stabbing several people. Five people were killed and 40 others injured. (Stefan Wermuth/Reuters)

Jan. 8, 2017: Four soldiers aged 20 to 22, three female and one male, were killed and several other injured after the driver of a semi-trailer truck targeted Israel Defence Forces at an esplanade in East Jerusalem. The Palestinian driver, identified as 28-year-old Fadi al-Qunbar was shot dead.

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A car rammed intentionally rammed into a pedestrian mall in Melbourne, Australia, in January, killing four people and injuring 20 others. (Edgar Su/Reuters)

Dec. 19, 2016: A young Tunisian rammed a truck into a crowded Berlin Christmas market, killing 12 and injuring dozens in an attack claimed by the Islamic State group. It was the first mass casualty attack by Islamic extremists carried out on German soil. Attacker Anis Amri, who had been denied asylum in Germany, was killed by police in Italy after an international manhunt.

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This frame grab from video, shows Israeli emergency services personnel covering bodies with plastic sheets at scene of a truck-ramming attack in East Jerusalem that killed four on Jan. 8. (Associated Press)

July 14, 2016: A Tunisian residing in France plowed a refrigerator truck through a crowd celebrating Bastille Day on the Mediterranean beachfront in Nice, killing 86. Attacker Mohamed Lahouaiej Bouhlel was killed by police. Cities around the world beefed up measures to prevent vehicle attacks in response. ISIS claimed responsibility for the attack, but to date, a recent GQ investigation noted, no pledge of allegiance from Bouhlel to the group has been discovered.

Dec. 21, 2014: A motorist injured 13 pedestrians in the French city of Dijon; a day later, a man ran over pedestrians at a Christmas market in Nantes in western France, killing one and injuring nine. Both suspects, who survived, had histories of mental illness.

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A truck crashed through a Christmas Market in Berlin in December 2016, leaving 12 people dead.

Oct. 20, 2014: A 25-year-old man drove his car into Canadian Air Force members near Montreal, killing one of them and injuring another. Authorities said the driver was a convert to Islam and had been flagged for jihadist ambitions. He was later shot dead by police.

June 30, 2007: Two men attempted to crash a blazing Jeep loaded with explosives into Glasgow Airport in Scotland. The car's path was blocked and the explosives failed to detonate.

Clarifications

  • An original version stated that the Nice attack killer pledged allegiance to ISIS. In fact, while ISIS claimed responsibility, in contrast to other notable attacks, no statement or video of allegiance from Bouhlel has been produced to date.
    Mar 22, 2017 11:32 PM ET
With files from Reuters and The Associated Press