Iran said on Saturday its armed forces ‘unintentionally’ shot down a Ukrainian passenger jet that crashed after taking off from Tehran, killing all 176 people aboard. President Hassan Rouhani said a military investigation had found ‘missiles fired due to human error’ brought down the Boeing 737 on Wednesday, calling it an ‘unforgivable mistake’. The about-turn came after officials in Iran had categorically denied Western claims that the Ukraine International Airlines (UIA) airliner had been struck by a missile in a catastrophic error. The plane, which had been bound for Kiev, slammed into a field shortly after taking off from Tehran’s Imam Khomeini International Airport before dawn on Wednesday. It came only hours after Iran’s armed forces launched a wave of missiles at bases hosting American forces in Iraq in response to the killing of Qasem Soleimani, one of Iran’s top generals, in a US drone strike. Iran had come under mounting pressure to allow a ‘credible’ investigation after video footage emerged appearing to show the plane being hit by a fast-moving object before a flash appears. The Ukrainian and Canadian leaders called for accountability after Iran’s admission. The armed forces were first to acknowledge the error, saying the Boeing 737 had been mistaken for a ‘hostile plane’ at a time when enemy threats were at the highest level. “The Islamic Republic of Iran deeply regrets this disastrous mistake,” Rouhani said on Twitter. “Armed Forces’ internal investigation has concluded that regrettably missiles fired due to human error caused the horrific crash of the Ukrainian plane & death of 176 innocent people.” In a statement posted on the government’s website, Rouhani said Iran’s armed forces had been on alert for possible attacks by the Americans after the martyrdom of Soleimani. Iranian President Hassan Rouhani tweeted that the Islamic Republic of Iran deeply regrets this disastrous mistake’ after the downing of the Ukrainian airliner on Wednesday “Iran is very much saddened by this catastrophic mistake and I, on behalf of the Islamic Republic of Iran, express my deep condolences to the families of victims of this painful catastrophe,” he said. Rouhani added that he had ordered ‘all relevant bodies to take all necessary actions (to ensure) compensation’ to the families of those killed. “This painful incident is not an issue that can be overcome easily,” he said, adding that the perpetrators of the unforgivable mistake will be prosecuted. “It is necessary to take necessary steps and measures to remove the weak points of the country’s defence systems so that such a catastrophe is never repeated again,” he said. The majority of passengers on UIA Flight PS752 were dual national Iranian-Canadians but also included Ukrainians, Afghans, Britons and Swedes. Ukrainian President Volodymyr Zelensky demanded Saturday that Iran punish those responsible for the downing of the plane and pay compensation. “We expect Iran… to bring the guilty to the courts,” the Ukrainian leader wrote on Facebook. Canadian Prime Minister Justin Trudeau said closure and accountability were needed in the wake of the incident. He also demanded ‘transparency, and justice for the families and loved ones of the victims’. “This is a national tragedy, and all Canadians are mourning together,” his office said in a statement. “Human error at time of crisis caused by US adventurism led to disaster,” Iranian Foreign Minister Mohammad Javad Zarif tweeted. “Our profound regrets, apologies and condolences to our people, to the families of all victims, and to other affected nations.”