Canada Prime Minister Justin Trudeau said on Thursday multiple intelligence sources indicate that Iran shot down a Ukrainian airliner after it took off from Tehran, killing all 176 on board, including 63 Canadians.

Mr. Trudeau’s comments came as video emerged that appeared to show the moment the airliner was hit.

That and other footage posted on social media increasingly pointed to a catastrophic mistake by Tehran’s air defense batteries in bringing down Ukraine International Airlines Flight PS752 early on Wednesday.

The video, which The New York Times said it verified, shows a fast-moving object rising at an angle into the sky before a bright flash is seen, which dims and then continues moving forward. Several seconds later an explosion is heard.

Citing information from allies as well as Canada’s own intelligence, Mr. Trudeau said the plane appeared to have been hit by an Iranian surface-to-air (SAM) missile.

“We know this may have been unintentional. Canadians have questions, and they deserve answers,” Mr. Trudeau told reporters.

The U.S. National Transportation Safety Board late on Thursday said it had received formal notification of the crash from Iran and would send a representative to join the crash probe.

Iran’s Foreign Ministry earlier invited the U.S. plane maker Boeing to “participate” in the inquiry.

Mr. Trudeau said Canada was working with allies to ensure a credible probe. “The families of the victims want answers, Canadians want answers, I want answers,” he said.

With tensions high between the U.S. and Iran, the disaster unfolded just hours after Tehran launched ballistic missiles towards bases in Iraq housing U.S. troops.

Ukraine called for United Nations support for a broad investigation, and sent 45 crash investigators to Tehran to take part in the inquiry led by Iranian authorities.

“If any country has information that can help conduct a transparent and objective investigation into the tragedy, we are ready to receive it and cooperate in further verification,” the Ukraine presidency said in an English-language statement.

Tehran denies

Iran’s civil aviation chief denied on Friday that a missile downed the Ukrainian airliner, dismissing claims of a catastrophic mistake by Tehran’s air defences.

“One thing is for certain, this airplane was not hit by a missile,” Iran’s civil aviation chief Ali Abedzadeh said, adding that “any remarks made before the data is extracted (from the plane's black box flight recorders) ... is not an expert opinion.”

Mr. Abedzadeh said Tehran had invited “Americans, Canadians, the French, Ukrainians and the Swedish” to be present during the investigations, showing that “we are honest in our procedure”. He said the missile theory could not be “scientifically correct” because it was not possible for an airliner to be hit and “continue flying for 60 to 70 seconds”.

And “the debris collected has been in a very limited area. If there was an explosion in the wings it should have been much more scattered,” Mr. Abedzadeh added, noting that analysing the black box data “will take time”.