Canada’s Prime Minister has said he has intelligence indicating that a passenger jet that crashed in Iran this week was shot down.

Justin Trudeau said the information comes from “multiple sources, including our allies and our own intelligence.”

All 176 people on board the Ukraine International Airlines flight were killed after it came down near Tehran on Wednesday.

There were 63 Canadians among the dead.

“The evidence indicates that the plane was shot down by an Iranian surface-to-air missile,” said Mr Trudeau. “This may well have been unintentional.”

He described the crash as “tragedy that not only shocked Canada, but the rest of the world.”

"The news will undoubtedly come as a further shock to the families who are already grieving," he said.

He said the intelligence “reinforces the need for a thorough investigation into this matter.”

It comes after US officials said they are “confident” the plane was shot down.

Workers at the air crash site of a Boeing 737 Ukrainian passenger plane near Tehran, Iran, 08-01-2020. Image: Ahmad Halabisaz/Xinhua News Agency/PA Images

US President Donald Trump said he ‘has his suspicions’ – but noted that “somebody could have made a mistake on the other side.”

The Reuters news agency reported a US official as saying satellites had detected the launch of two missiles shortly before the plane crashed, followed by evidence of an explosion.

Two other officials said Washington believed the downing of the Ukraine International Airlines plane was accidental.

Meanwhile, Downing Street in London said it was looking into “very concerning” reports that the Ukrainian plane was shot down.

Iran's head of civil aviation has dismissed the idea the plane was hit by a missile as “impossible.”

Debris is seen from a plane crash on the outskirts of Tehran, Iran | Image: Mohammad Nasiri/AP/Press Association Images

Earlier today Oleksiy Danilov, secretary of Ukraine's Security Council said a missile strike, possibly from a Tor missile is among the main theories for the cause of the crash.

The Iranian military makes use of the Russian-made Tor system.

He said “information had surfaced on the internet about elements of a missile being found” near the crash site.

Ukrainian officials have arrived in Iran but have not yet been given permission to examine the site.

US President Donald Trump at the White House, 09-01-2020. Image: AP Photo/ Evan Vucci

Asked this evening what he thought happened to the plane, US President Donald Trump said: “Well I have my suspicions.”

“I don’t want to say that because other people have their suspicions also.

“But somebody could have made a mistake on the other side. It was flying in a pretty rough neighbourhood and somebody could have a mistake.

“Some people say it was mechanical. I personally don’t think that is even a question personally.”

Asked if he thought it could have been shot down by accident he said: “I don’t know. That is up to them.”

“At some point they will release the black box. Ideally they would give it to Boeing but if they give to France or if they gave it to some other country, that would be OK too.”

Mr Trudeau said Tehran had indicated it will keep the black boxes in Iran – but will allow Ukrainian investigators access.

He said Canada will not rest until it gets closure, transparency, accountability and justice, but that it is too soon to be “apportioning blame for the crash.”

Debris is seen from a plane crash on the outskirts of Tehran, Iran | Image: Mohammad Nasiri/AP/Press Association Images

Following a call between the UK Prime Minister Boris Johnson and the Ukraine President Volodymyr Zelenskiy this afternoon, Downing Street called for a “full credible and transparent investigation.”

A spokesman said reports seen by UK officials “are very concerning.”

Mr Danilov said the three other possible causes of the crash under consideration include a drone or "other flying object" crashing into the plane mid-air, an explosion on the plane "as a result of a terrorist attack" or an engine malfunction causing the engine to explode.