Iran’s head of aviation says he is “certain” a missile did not bring down a passenger plane as it left the capital Tehran, killing more than 170 people.

It came after Western leaders claimed to have found evidence the Ukraine International Airlines flight PS752  had been accidentally hit by a surface-to-air missile - just hours after the state carried out missile strikes on two airbases housing US forces in Iraq.

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Reports in the US media suggested the airliner was struck by a missile after being mistaken for a warplane.

However, at a news conference on Friday Iran's Civil Aviation Organisation (CAOI) chief Ali Abedzadeh said this was not the case.

He told reporters: “The thing that is clear to us and that we can say with certainty is that this plane was not hit by a missile.”

"As I said last night, this plane for more than one and a half minutes was on fire and was in the air, and the location shows that the pilot was attempting to return."

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Black box recorders from the flight are set to be opened on Friday, according to Iran’s IRNA news agency.

Nationals from the UK, Iran, Canada, Sweden, Afghanistan, Germany and Ukraine were among 176 people who lost their lives in the tragedy.