Speaking at a memorial service for the 57 Canadian passengers who died, the prime minister of Canada said the tragedy should never have happened.
“We will not rest until there are answers,” he said at the vigil in Edmonton. “We will not rest until there is justice and accountability.”
After several days of denials, Iran has now admitted its military forces accidentally shot down Ukrainian International Airlines Flight 752.
It said a Revolutionary Guard anti-aircraft defence unit was on high alert after Iran had fired missiles at US bases in Iraq – in retaliation for the assassination of Qassem Soleimani – and mistook the scheduled passenger jet for a US attack.
The president of Iran, Hassan Rouhani, said his nation “deeply regrets this disastrous mistake” and pledged there would be a full investigation.
Mr Trudeau said Canada would play a part in finding out the truth about the accident.
Addressing a crowd of thousands inside a university gym, he said: “I want to assure you that you have my full support during this extraordinarily difficult time... you give us purpose to pursue justice and accountability for you.”
Thirteen of the Canadian victims came from the city of Edmonton and tearful tributes to them were read out during the vigil.
One friend of a father who was killed in the disaster along with his wife and two daughters said the loss was “too much to bear”.
Public grief was also expressed at other vigils across Canada. At the University of Toronto, many in the crowd openly wept as the names of the victims were read out one by one.
Iran has invited Canadian experts to join their investigation, and three officials have already arrived with visas for eight others also approved.
Canada’s Transportation Board has also said it will send a team of investigators who specialise in retrieving and analysing data from aeroplane black boxes.
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