Security experts say Canada is at risk of homegrown terrorists using vehicles as weapons, following the London attack and reports that a Canadian suspected of ties to ISIS has been arrested in Turkey.

In Tuesday’s London attack, 52-year-old Khalid Masood used a rented car to strike pedestrians on Westminster Bridge before crashing the vehicle into a gate. He then fatally stabbed a police officer just outside the British parliament.

Less than 24 hours later, prosecutors in Antwerp said police narrowly stopped a vehicle attack on a popular shopping area, with a French resident behind the wheel.

Europe has seen several high-profile terror attacks involving vehicles in recent years, including the 2016 Nice attack, when a Tunisian resident of France drove a cargo truck into crowds of people and left 86 dead.

Security experts warn that such attacks are difficult to prevent.

“Anybody could be walking down the street and all of a sudden this vehicle decides your time is up and goes on the sidewalk, and could attack and kill a number of innocent bystanders,” said former RCMP deputy commissioner Pierre-Yves Bourduas.

Canada has already seen such violence: the October 2014 murder of Warrant Officer Patrice Vincent. He was run down and killed by a man who pledged allegiance to the Islamic State.

Experts say homegrown terrorism is the number one threat to Canada’s national security.

“There are hundreds of individuals at any one time that CSIS is well aware of, that are actively engaged at quite advanced level,” said Lorne Dawson, a professor of sociology at the University of Waterloo.

Michael Zehaf Bibeau, the gunman who attacked Parliament Hill, and would-be suicide bomber Aaron Driver were both Canadian-born and self-radicalized.

“ISIS, through its spokespeople for two or three years now, has been calling for these direct attacks,” said Dawson.

Finding and monitoring potential self-radicalized terrorists poses a serious challenge for intelligence agencies.

Despite those concerns, the federal government gave little new money for counter-terrorism measures in the federal budget this week.

“The Canadian national security apparatus, including defence, RCMP, the intelligence agencies and border security are grossly under-resourced in this country,” said former Special Forces commander Steve Day.

“There’s not enough people; there’s not enough money.”

With a report by CTV’s Mercedes Stephenson in Ottawa