TORONTO (WASHINGTON POST, REUTERS) - A 25-year-old suspect accused of mowing down pedestrians with a van in a busy Toronto shopping district was ordered held on Tuesday (April 24) on 10 counts of first-degree murder - one of each of the victims in an attack whose motives still remain unclear.

Authorities said Monday's carnage did not trigger a national security threat, suggesting it was not initially viewed as having possible terrorism links.

But investigators have not offered further details on what may have led the suspect, Alek Minassian, to plough the rented van through crowds on a warm spring afternoon - claiming at least 10 lives and leaving more than a dozen others injured.

Minassian is said to have left a "cryptic message" on social media before his attack.

Facebook confirmed that the suspect wrote a post before the incident that referenced an "incel rebellion". The term is shorthand used on some online message boards for "involuntary celibacy", a loose social media movement of men who blame women for their celibacy.

Canadian authorities have declined to say whether anger towards women motivated the attack.

The post also voiced admiration for a man who killed six college students before taking his own life in California in 2014 and who cited the "cruelness of women" for his virgin status.

"The accused is alleged to have posted a cryptic message on Facebook minutes before" the attack, Graham Gibson, a Toronto police detective sergeant, told a news conference.

The majority of the victims were women, ranging in age from their mid-20s to early 80s, Gibson said. He said the question of whether the attack was driven by anger against women was "going to be part of our investigation."

Facebook has since deleted Minassian's account, a representative said. "There is absolutely no place on our platform for people who commit such horrendous acts," she said in an email.

In a Toronto court, Minassian wore a white prison jumpsuit with his hands cuffed behind his back. The judge read the charges, which also included 13 counts of attempted murder.

Minassian confirmed his name for the court. He then answered "yes" when asked if he understood a court order not to have any contact with the victims or their families.

The next hearing was scheduled for May 10. Minassian was ordered held pending a possible bail hearing.

In the meantime, officials will attempt to piece together the planning and motives for a suspect who was not previously on any law enforcement watch lists. Witnesses said the van jumped a curb and roared through a crowded pedestrian zone in what appeared to be a deliberate act.

In a news conference, Prime Minister Justin Trudeau said the incident was a "senseless attack and a horrific tragedy." But he noted that authorities see no national security element in the attack, which carried hallmarks of previous vehicle-as-weapon assaults in New York and several European cities.

Trudeau added that the attack "hasn't changed the overall threat level in Canada" although it took place as envoys from the Group of Seven industrialised nations met in Toronto.

Meanwhile, the first victim to be publicly identified was named as Anne Marie D'Amico, an employee at the investment management firm Invesco, which has its Canadian headquarters on Yonge Street, where the attack occurred.

"I can now confirm that unfortunately one of our employees has succumbed to her injuries," Peter Intraligi, president of Invesco Canada, said in a statement. "Our thoughts and prayers continue to be with all those impacted by this tragic event."

Toronto's police chief identified the driver as Minassian, of Richmond Hill, Ontario. Minassian, who was not carrying a weapon, was taken into custody after a showdown in which he brandished an object and told officers, "Shoot me in the head."

"On the basis of all available information at the present time, there would appear to be no national security connection to this particular incident," Canada's minister of public safety minister, Ralph Goodale, said late Monday.

"The events that happened on the street behind us are horrendous, but they do not appear to be connected in any way to national security based on the information at this time."

Toronto's police chief, Mark Saunders, said nothing was being ruled out, and Minassian was not previously known to police.

The incident had echoes of vehicle attacks in the French city of Nice, as well as in London, Berlin and New York City - a method that the Islamic State in Iraq and Syria (ISIS) militant group has encouraged followers to use.

"We lost a little bit of our innocence," John Filion, a city council member who represents the area where the incident occurred, said in a phone interview Monday.

"We often think of ourselves as being somewhat excluded from the violence and craziness that goes on in other parts of the world. You just kind of don't think of Toronto as a place where that kind of violence will come to."

The attack took place in the center of North York, a part of Toronto that has grown over the past two decades into a secondary downtown.

The area is so busy that Toronto's city council earlier this year debated widening the sidewalks and reducing lanes of traffic to make it more pedestrian-friendly.

"He started going down on the sidewalk and crumbling down people one by one," Ali Shaker, who was in the vicinity of the incident, told CTV News. "He just destroyed so many people's lives."

He said the driver was travelling at an estimated 55kmh to to 70kmh.

While Canadians are proud of living in a country where crime rates are generally low and ethnic diversity is celebrated rather than feared, several terrorism-related incidents in recent years have reminded the public that Canada is not immune to the kinds of events that have struck Europe and the United States.

In September, Abdulahi Hasan Sharif was arrested in Edmonton, Alberta, after two related incidents on the same evening. In the first one, Sharif, a Somali refugee, is alleged to have rammed into a police officer who was at a police roadblock near a sports event. He then stabbed the police officer and escaped. A few hours later, the same man is alleged to have rammed into four pedestrians with a rental van. No one was killed, but Sharif faces multiple counts of attempted murder.

In Quebec City, Alexandre Bissonnette is in court this week for a sentencing hearing after pleading guilty last month to six counts of first-degree murder in the shooting of six Muslim men as they attended prayers at a mosque in the city in January 2017. Bissonnette had mental health issues and was attracted to far-right politics and anti-immigrant rhetoric.

And in 2014, Canada's Parliament was the scene of another terrorism-related incident. Michael Zehar-Bibeau, a drug addict and convert to Islam, shot and killed a Canadian sentry on duty at the National War Memorial before heading to Parliament, where he was killed in a shootout with security officers.