As Canada 150 crowds in Toronto sang along with the Barenaked Ladies and Drake or watched fireworks in Nathan Phillips Square, they were being protected by strategically placed dump trucks, buses and street cleaning machines meant to prevent a vehicular attack.

Police forces and city officials across the country are boosting security measures, including repurposing heavy vehicles, at festivals and concerts in the wake of international terrorist attacks in which vehicles have been used as weapons.

Over the weekend, police and officials parked a heavy city dump truck and a TTC bus at the intersection of Yonge Street and Queen Street. Two more dump truck-bus pairs were placed on Bay Street and further west on Queen near University Avenue. Street cleaning vehicles were positioned along the stretch of Queen Street that was closed for the long-weekend celebrations.

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Toronto Police spokesman Mark Pugash confirmed that his service had adopted the strategy within the last few months for large events.

"We constantly review our security plans and change them as necessary," he said. "This is one of the adjustments that we make when we believe it's necessary, taking into account all the factors that we deal with."

Mr. Pugash said Toronto Police are in constant contact with other law-enforcement and intelligence agencies in Canada and around the world, monitoring for possible threats to the city. He added that police have made other security changes "behind the scenes" that he could not discuss.

In addition to the use of city vehicles as roadblocks during the Canada 150 weekend events in Toronto, the tactic was also evident on June 25 during Toronto's Pride Parade. Besides a police cruiser, a city bus was parked blocking Dundas Street at Bay Street as large crowds gathered at nearby Yonge-Dundas Square, where the parade ended.

The extra security measures come in the wake of attacks elsewhere in the world using vehicles, most recently in Finsbury Park and at London Bridge in Britain in June, as well as earlier attacks in Stockholm, Westminster, Jerusalem, Nice and Berlin.

Twelve people in Germany were killed in the Berlin Christmas market attack last December, which resulted in managers of the Christmas market in Toronto's Distillery District requesting more paid-duty police officers and installing concrete barriers to block vehicles.

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On Tuesday, Radio-Canada reported it had obtained a 25-page document from Montreal police that indicated the force is stepping up efforts to protect people taking part in summer festivals and outdoor events.

Montreal police spokeswoman, Marie-Élaine Ladouceur, confirmed that the use of heavy vehicles and other tactics are being considered for events at which large crowds are expected this summer in the Quebec city.

"Using vehicles is one of our strategies, but it's not the only possibility, we can also use concrete blocks," Ms. Ladouceur said. "The goal is to make these sites less vulnerable."

In Ottawa, tractors and dump trucks blocked roads and entrance ways leading to Parliament Hill on Canada Day. Heading into the festivities, Ottawa Mayor Jim Watson said attacks around the world where vehicles have been used should act as a "wake-up call" for leaders to be vigilant and that a "motor vehicle can be the new weapon of choice for a terrorist or for someone who wants to cause harm to people."

A spokesperson for Calgary's police service also alluded to the possible use of heavy vehicles to block major roadways and thoroughfares when the 2017 Calgary Stampede starts this weekend.

In Newfoundland and Labrador, Constable Geoff Higdon of the Royal Newfoundland Constabulary wouldn't say if the RNC was planning to use heavy trucks or buses to block the entrance to the busy George Street Festival at the end of July in St. John's. He said security priorities were different for smaller provinces and cities than for larger centres such as Toronto, Montreal, Ottawa or Calgary.

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"We do not as of yet use this process in Newfoundland and Labrador but we do monitor major protests and festivals from an intelligence perspective and assign additional resources as required," Const. Higdon said.

Officers with both the Halifax Regional and Vancouver Police Departments said they do not discuss the operational plans of their forces for fear of jeopardizing the security of those they aim to protect.

With files from Canadian Press