Iran has admitted its military made an “unforgivable mistake” in unintentionally shooting down a Ukrainian jetliner and killing all 176 people onboard, after days of rejecting western intelligence reports that pointed to Tehran being responsible.

A military statement on state TV early on Saturday blamed “human error” for the downing of Ukraine International Airlines flight 752 on Wednesday in the tense aftermath of strikes on US targets. It was followed by an apology from Iran’s president and condolences from the supreme leader, Ayatollah Ali Khamenei.

Ukraine’s president, Volodymyr Zelenskiy, responded on Saturday morning that Iran must make an official apology and agree to a full investigation and compensation, as well as cooperating with Ukraine’s own investigators. “Our 45 professionals should have full access and cooperation to establish justice,” a statement from the presidency said.

The Canadian prime minister, Justin Trudeau ,also said his country’s focus remained on “closure, accountability, transparency and justice” for the families of the 57 Canadian victims.

Hassan Rouhani, the Iranian president, wrote on Saturday: “The Islamic Republic of Iran deeply regrets this disastrous mistake. My thoughts and prayers go to all the mourning families. I offer my sincerest condolences.”

Hassan Rouhani (@HassanRouhani) The Islamic Republic of Iran deeply regrets this disastrous mistake.



My thoughts and prayers go to all the mourning families. I offer my sincerest condolences. https://t.co/4dkePxupzm

The Iranian foreign minister, Javad Zarif, wrote: “A sad day. Preliminary conclusions of internal investigation by armed forces: human error at time of crisis caused by US adventurism led to disaster. Our profound regrets, apologies and condolences to our people, to the families of all victims, and to other affected nations.”

The plane was mistaken for a hostile target after it turned towards a sensitive military centre of the Revolutionary Guards, according to the military statement, carried on the official IRNA news agency.

“The military was at its highest level of readiness” amid the heightened tensions with the US, it said, adding: “In such a condition, because of human error and in an unintentional way, the flight was hit.”

The military apologised for the disaster and said it would upgrade its systems to prevent such mistakes in the future. The responsible parties would be referred to a judicial department within the military and held accountable, it said.

Javad Zarif (@JZarif) A sad day. Preliminary conclusions of internal investigation by Armed Forces:



Human error at time of crisis caused by US adventurism led to disaster



Our profound regrets, apologies and condolences to our people, to the families of all victims, and to other affected nations.

💔

A fuller explanation and apology would be forthcoming from Iran’s Revolutionary Guards later on Saturday, IRNA news reported, citing an informed source within the Guards.

The jetliner, a Boeing 737-800, went down on the outskirts of Tehran during takeoff a few hours after Iran had launched a barrage of missiles at US forces in Iraq in the early hours of Wednesday.

The strikes on two US bases were in retaliation for the US drone strike that killed the al-Quds force leader, Qassem Suleimani, in Baghdad on 3 January – the culmination of a recent series of tit-for-tat attacks that threatened to push Washington and Tehran into war.

Play Video 3:40 Why did Trump order the killing of Iran's Qassem Suleimani? – video explainer

Iran’s acknowledgement of responsibility renews questions of why authorities did not shut down the country’s main international airport and its airspace after launching ballistic missile attacks, when they feared US reprisals were possible.

It also undermines the credibility of information provided by senior Iranian officials so far. As recently as Friday, Ali Abedzadeh, the head of the national aviation department, told reporters with certainty that a missile had not caused the crash. On Thursday, the cabinet spokesman Ali Rabiei had also dismissed reports of a missile strike.

Zelenskiy said: “Even before the termination of the International Commission, Iran has pleaded guilty to crashing the Ukrainian plane. But we insist on full admission of guilt. We expect from Iran assurances of readiness for full and open investigation, bringing those responsible to justice, returning the bodies of the dead, payment of compensation, official apologies through diplomatic channels.”

The acknowledgement is also likely to inflame public sentiment inside the country against authorities after Iranians had rallied around their leaders following Suleimani’s killing. The general was seen as a national icon and hundreds of thousands of people turned out for funeral processions across the country.

Iran admits shooting down Ukrainian airliner 'unintentionally' – state TV Read more

The vast majority of the crash victims were Iranians or Iranian-Canadians, however, and it came just weeks after authorities quashed nationwide protests ignited by a hike in fuel prices.

“This is the right step for the Iranian government to admit responsibility, and it gives people a step toward closure with this admission,” said Payman Parseyan, a prominent Iranian-Canadian in western Canada who lost a number of friends in the crash. “I think the investigation would have disclosed it whether they admitted it or not. This will give them an opportunity to save face.”

Iran had denied for several days that missiles could have downed the aircraft and instead blamed a mechanical malfunction.

Western security officials began briefing on Thursday afternoon that intelligence suggested the plane had been accidentally shot down by two surface-to-air missiles fired by the Iranian military.

Play Video 0:31 Iran video appears to show missile striking Ukrainian plane – video

A preliminary report released by Iran’s civil aviation authority the day after the crash found that the pilots of the doomed plane did not make radio contact but had attempted to turn back to the airport before the plane went down.

Experts raised serious concerns over the handling of the crash site, such as over the removal of debris, prompting fears that Tehran had sought to eliminate evidence from the area.

Iran has invited investigators from Canada and Ukraine and from Boeing to visit the crash site on the outskirts of Tehran and said it would also welcome representatives of other countries whose citizens were killed.

The plane, en route to the Ukrainian capital, Kyiv, was carrying 167 passengers and nine crew members from several countries, including 82 Iranians, at least 57 Canadians, 11 Ukrainians and three Britons.

Iran had said on Thursday it would download information from voice and flight data recorders, known as black boxes, to determine what had happened, although it said the process could take up to two months. The Ukrainian foreign minister, Vadym Prystaiko, said on Friday that Kyiv had been given access to the flight recorders and planned to start analysing their content.

Experts said mounting international scrutiny would have made it all but impossible to hide signs of a missile strike during any investigation and Tehran may have felt it best to make a swift policy reversal than battle rising criticism abroad.

With Reuters and the Associated Press