No clear motive behind Toronto van attack as suspect Alek Minassian charged

The man accused of ploughing a rental van into pedestrians on a crowded Toronto sidewalk in Canada's deadliest mass killing in decades has been charged with 10 counts of first-degree murder as police probe what motivated his rampage.

Suspect Alek Minassian, 25, was also charged with 13 counts of attempted murder for the incident that had the hallmarks of deadly vehicle assaults by Islamic State supporters, but Prime Minister Justin Trudeau said there was no reason to suspect any national security connection.

Minassian kept his shaved head down during a brief court appearance in Canada's largest city, speaking quietly with a defence lawyer and stated his name in a steady voice when asked to do so.

Canadian media cited one possible clue to his motive: a Facebook post by Minassian shortly before the incident that referenced an "incel rebellion," a shorthand used in some online message boards for "involuntary celibacy." The Toronto Globe and Mail reported the post, citing a spokeswoman for the social media company.

The post also voiced admiration for a man who killed six college students before taking his own life in California in 2014.

Trudeau called on all Canadians to stand united with Toronto as flowers and scrawled messages in multiple languages piled up at a makeshift memorial in the city's north end, an ethnically diverse neighbourhood of towering office buildings, shops, restaurants and homes.

"We cannot as Canadians choose to live in fear every single day as we go about our daily business," Trudeau said outside parliament in Ottawa.

The prime minister said the incident had not changed the country's threat level or security preparations for a G7 summit in Quebec in June.

The Canadian flag was lowered to half-mast at parliament and at Toronto city hall.

Minassian had briefly served in Canada's armed forces in late 2017 but asked to be voluntarily released after 16 days of training, defence ministry spokeswoman Jessica Lamirande said.

He had previously attended a high school program where one classmate remembered him as "absolutely harmless."

The suspect's two-story red-brick home in a suburb north of Toronto was a crime scene Tuesday, taped off and surrounded by police vehicles. Officers went in and out of the house.

Details about the dead began to emerge on Tuesday, with a South Korean foreign ministry representative saying that two of that country's citizens were killed and one injured in the attack. Jordan's embassy also said one of its citizens was among the victims.

The attack shook the usually peaceful streets of Toronto, a multicultural city with a population of 2.8 million. The city recorded 61 murders last year.

Canada is still recovering from the shock of a highway crash in Saskatchewan earlier this month that killed 16 people on a bus carrying a junior hockey team.