Canadian Prime Minister Justin Trudeau said it has been gut-wrenching to listen to stories from relatives of 57 Canadians who died in the downing of a Ukrainian jetliner in Iran.

Speaking at a memorial with a capacity crowd of 2,300 in Edmonton, Alberta, Mr Trudeau said he has learned many of the victims came to Canada in search of new opportunities for their families, but those families are now consumed by grief and outrage.

The plane was shot down by an Iranian missile moments after taking off from Tehran on Wednesday. All 176 people on board were killed, including 138 who were headed for Canada.

Iran has admitted the plane was mistaken for a hostile target amid soaring tensions with the United States.

Mr Trudeau called it a Canadian tragedy.

“This tragedy should never have occurred,” he said. “We will not rest until there are answers. We will not rest until there is justice and accountability.”

Other memorials were held across the country.

At the Vancouver Art Gallery, national defence minister Harjit Sajjan also called the crash a national tragedy. At the University of Toronto, many cried throughout the ceremony as speakers listed victims, including a one-year-old child.

Iran plane crash graphic
(PA Graphics)

Fati Mortazavi, whose best friend died in the crash, said having a community come together helped her cope with the tragedy.

Three members of Canada’s Standing Rapid Deployment Team arrived in Iran on Saturday to establish a base of operations for the Canadian government in the wake of the crash.

Foreign affairs minister Francois-Philippe Champagne said that Iran has approved visas for six more members of the team, who are currently in Ankara, Turkey, as well as for two experts from the Transportation Safety Board.

A spokesman for Mr Champagne said the officials “will be there to provide consular assistance to the families of the victims, including supporting repatriation of remains, to help identify victims and to assist in the investigation”.

Iran plane crash
People gather for a vigil to remember the victims of the plane crash in Tehran (Ebrahim Noroozi/AP)

Canada’s Transportation Board said it also plans to deploy a second team of investigators who specialise in aircraft recorder download and analysis.

Meanwhile, online videos have emerged purporting to show Iranian police and security forces firing live ammunition and tear gas to disperse demonstrators protesting against the Islamic Republic’s initial denial that it shot down the plane.

International rights groups have called on Iran to allow people to protest peacefully as allowed by the country’s constitution.

“After successive national traumas in a short time period, people should be allowed to safely grieve and demand accountability,” said Hadi Ghaemi, the executive director of the New York-based Centre for Human Rights in Iran.

“Iranians shouldn’t have to risk their lives to exercise their constitutional right to peaceful assembly.”