(Update 1: adds Nato angle, alters headline, lede accordingly)

By Marina Villén

Tehran, Jan 10 (EFE).- The secretary-general of Nato, Jens Stoltenberg, on Friday said he believed the Ukrainian International Airlines flight that crashed after takeoff from Tehran airport killing all 176 on board could have been shot down by an Iranian missile.

"I won't go into details about our intelligence, but we have no reason not to believe the reports we have seen from different Allied capitals," Stoltenberg told press as he arrived for a meeting of European foreign ministers in Belgium.

"They have expressed concern about information indicating that the plan may have been downed by Iranian air defense systems. That's exactly why we need a thorough investigation."

He urged full cooperation from the Iranian side.

His comments came after the US, Canada, the Netherlands and Luxembourg, all Nato members, said they believed UIA Flight PS752 was accidentally shot down by an Iranian missile on Wednesday. Earlier, the head of Iran's Civil Aviation Organisation dismissed suggestions the UAI flight was downed by Iran's military.

At a press conference in Tehran, Ali Abedzade urged people to wait for the results of information contained on the black box flight recorders from the plane which crashed on Wednesday.

"One thing is for certain, this airplane was not hit by a missile," Abedzadeh said. "Any remarks made before the data is extracted is not an expert opinion."

The previous evening, Canadian Prime Minister Justin Trudeau said his government had intelligence indicating otherwise.

Trudeau said Canadian officials believe that the supposed shootdown of the Boeing 737-800 airliner "may have been unintentional."

At least 63 Canadians, mostly of Iranian origin, were traveling on the plane bound for Kiev. The aircraft crashed shortly after take off from Tehran's Imam Khomeini International Airport.

Preliminary information and videos posted online suggest the plane was on fire and had turned back round toward the airport before it crashed.

But Ukrainian prime minister Volodymyr Zelensky said that while this theory had not been ruled out, Iran's involvement or responsibility in the incident had yet to be confirmed.

Zelensky also urged his country's "international partners", including the governments of the United States, Canada and the United Kingdom - "to provide data and evidence" to the commission investigating the disaster.

Abedzadeh said that countries should submit any evidence and data they might have to the world and to the Iranian Civil Aviation Organisation.

During the press conference, he said: "there was a fire on the plane for more than a minute while it was in the air" and that the location of the crash "shows the pilot was trying to return (to Tehran's Imam Khomeini International Airport)."

Abedzadeh added that while Iran would be able to extract the data from the black boxes, which store, among other information, conversations between the pilots, Tehran would seek "help from other countries" during the process.

A team of Ukrainian experts is already working at the site to investigate the cause of the crash.

Prior to the accusations that the missile had been shot down, Iran's Foreign Ministry said it had invited Ukraine and manufacturer Boeing to take part in the investigations.

In a statement, the US National Transport Safety Bureau said it had received an invitation to take part.

The accident occurred shortly after the Middle Eastern country launched more than a dozen ballistic missiles at two US military bases in Iraq, in retaliation for the killing of Iranian General Qasem Soleimani in an airstrike in Baghdad on Jan. 3.

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EFE correspondents in Brussels and Kiev contributed to this text

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