This Jan 8, 2020 file photo shows debris at the scene where a Ukrainian plane crashed in Shahedshahr, southwest of the capital Tehran, Iran. EBRAHIM NOROOZI/AP)

DUBAI – Iran accused Western governments of engaging in “psychological warfare” in claiming the Boeing jet that crashed near Tehran on Wednesday was brought down by a missile, as the tragedy became further embroiled in geopolitical tensions.

“If they are certain and have the courage, they should share any finding that has scientific and technical backing,” Ali Abedzadeh, head of Iran’s Civil Aviation Organization, said in a televised briefing Friday.

If they are certain and have the courage, they should share any finding that has scientific and technical backing

 Ali Abedzadeh, head of Iran’s Civil Aviation Organization

The comments intensify a standoff over the crash, which came hours after Iran struck at US bases in Iraq in response to the killing of a top general. Canada, the UK and Australia all said they have intelligence showing the plane was shot down, while US sources have said two surface-to-air missile launches were detected soon after the Ukrainian jet took off, followed by an explosion.

Iran said on Friday it wanted to download black box recordings itself from the Ukrainian airliner, saying it could take one or two months to extract information from the voice and flight data recorders. It said it could ask Russia, Canada, France or Ukraine if it needed help.

Tehran also said the probe might take one or two years.

READ MORE: Iran says crashed jet tried to turn back as missile theory revives

Ukrainian President Volodymyr Zelenskiy said he could not rule out a missile strike but this had not been confirmed. Kiev has said its investigators wanted to search the crash site for any debris of a Russian-made missile used by Iran.

The Ukraine International Airlines flight to Kiev from Tehran crashed on Wednesday, when Iran was on alert for a US military response hours after firing missiles at US targets in Iraq. 

The incident adds to international pressure on Iran, after months of tension with the United States and then tit-for-tat military strikes. Washington killed an Iranian general last week in a drone attack in Iraq, prompting Tehran’s missile launches.

Canadian Prime Minister Justin Trudeau, citing intelligence from Canada and other sources, has blamed an Iranian missile for bringing down the plane that had 63 Canadians on board, although he said it “may well have been unintentional”

On social media, many Iranians voiced anger at the authorities for not closing the airport after Iran’s missile launches. Many passengers were Iranians with dual nationality.

“We prefer to download the black boxes in Iran. But if we see that we can’t do that because the boxes are damaged, then we will seek help,” Ali Abedzadeh, head of Iran’s Civil Aviation Organisation, told a news conference in Tehran.

ALSO READ: US-Iran distrust looms over Tehran air crash investigation

State television earlier showed the battered black boxes, saying their information could be downloaded and analyzed.

Canadian Prime Minister Justin Trudeau, citing intelligence from Canada and other sources, has blamed an Iranian missile for bringing down the plane that had 63 Canadians on board, although he said it “may well have been unintentional”.

“The evidence indicates that the plane was shot down by an Iranian surface-to-air missile,” he said.

Ukraine’s general prosecutor asked Canada “to provide information available to the Canadian side that may facilitate criminal investigations” into the crash.

ERROR

France’s BEA air accident agency said it would be involved in the investigation. BEA helped analyse data from the flight recorder of a Boeing that crashed in Ethiopia last year.

“It is important that as much clarity as possible is made and as quickly as possible,” French Foreign Minister Jean-Yves Le Drian said.

Candles sit in front of pictures of victims at a candlelight vigil to remember those killed in the Ukraine International Airlines plane crash, Jan 9, 2020, in Ottawa, Ontario. (ADRIAN WYLD / THE CANADIAN PRESS VIA AP)

The US National Transportation Safety Board (NTSB) has accepted an invitation from Iran to take part in its investigation.

The NTSB said in a statement its Response Operations Center had received formal notification from Iran of Wednesday's crash of the Boeing 737-800 that killed all 176 on board. 

"The NTSB has designated an accredited representative to the investigation of the crash," the agency said. 

A US official, citing satellite data, said Washington had concluded with a high degree of certainty that anti-aircraft missiles brought down the plane in error.

France’s BEA air accident agency said it would be involved in the investigation. BEA helped analyse data from the flight recorder of a Boeing that crashed in Ethiopia last year

The official said the data showed the plane airborne for two minutes after departing Tehran when heat signatures of two surface-to-air missiles were detected. There was an explosion in the vicinity and heat data showed the plane on fire as it fell. US military satellites detect infrared emissions from heat.

US President Donald Trump told reporters he believed “somebody could have made a mistake”.

A defence expert said the plane’s radar signature would have been similar to a US military transport plane.

The New York Times said it had obtained a video appearing to show an Iranian missile hitting a plane near Tehran airport.

COOPERATION

Iran denied the airliner had been hit by a missile, saying such reports were “psychological warfare against Iran.”

“All those countries whose citizens were aboard the plane can send representatives and we urge Boeing to send its representative to join the process of investigating the black box,” government spokesman Ali Rabiei said.

US President Donald Trump told reporters he believed “somebody could have made a mistake”

US, Canadian and French representatives were to travel to Tehran to attend meetings for the Iranian-led crash investigation, Iranian state media reported. Washington and Ottawa do not have diplomatic relations with Tehran.

Iran’s civil aviation organization said in an initial report less than 24 hours after the incident that the three-year-old airliner, which had its last scheduled maintenance on Monday, encountered a technical problem after takeoff and was heading to a nearby airport before it crashed.

IN PICTURES: Grief and mourning after Ukrainian plane crash in Iran

Investigations into airliner crashes require cooperation of regulators, experts and companies across jurisdictions. They can take months and initial reports in 24 hours are rare.

The Transportation Safety Board of Canada said it was making arrangements to tour the site after an Iranian invitation.

The US National Transportation Safety Board (NTSB) said it had designated a representative to join the probe.

Boeing said it would support the NTSB. The company is reeling from two deadly crashes of 737 MAX planes, including the one in Ethiopia, that led to the model’s grounding last year.

The crash plane was built in 2016 and is the prior generation of the 737 before the MAX.