Boris Johnson has welcomed Iran’s admission it unintentionally shot down the Ukrainian aircraft which crashed near Tehran as an “important first step”.
The Iranian government had previously denied claims it was responsible for bringing down the aircraft with the loss of all 176 passengers and crew – including four British nationals.
However after Britain, the US and Canada all said they believed it had been hit by surface-to-air missiles, President Hassan Rouhani acknowledged the plane had been struck “due to human error” in an “unforgivable” mistake.
Ukrainian International Airlines flight PS752 from Tehran to Kyiv came down on Wednesday, hours after Iran launched ballistic missiles at US bases in Iraq in revenge for the killing its top military commander, General Qassem Soleimani.
In a statement, the Prime Minister said there now needs to be a “comprehensive, transparent and independent international investigation” into exactly what happened.
He said the Government will do everything it can to support the families of the British victims and ensure they get “the answers and closure they deserve”.
He said: “Iran’s admission that Ukraine International Airlines flight 752 was shot down by mistake by its own armed forces is an important first step.
“We now need a comprehensive, transparent and independent international investigation and the repatriation of those who died.
“The UK will work closely with Canada, Ukraine and our other international partners affected by this accident to ensure this happens.
“This tragic accident only reinforces the importance of de-escalating tensions in the region. We can all see very clearly that further conflict will only lead to more loss and tragedy.
“It is vital that all leaders now pursue a diplomatic way forward.”
The majority of the crash victims were Iranians or Iranian-Canadians, while at least four of the victims are believed to be British nationals.
Canadian Prime Minister Justin Trudeau said his focus would be on securing “closure, accountability, transparency, and justice for the families and loved ones of the victims.”
Iran’s supreme leader Ayatollah Ali Khamenei offered condolences to the families of the victims and called for a full investigation.
He urged the armed forces to “pursue probable shortcomings and guilt in the painful incident”.
An Iranian Revolutionary Guard commander later said his unit accepted “full responsibility” for what happened.
In an address broadcast by state television, General Amir Ali Hajizadeh said that when he learned about the downing of the plane “I wished I were dead”.
A military statement carried by state media said the plane was mistaken for a “hostile target”, adding that the military was at its “highest level of readiness” amid heightened tensions with the US.
Mr Rouhani wrote on Twitter that an armed forces’ internal investigation had concluded that “missiles fired due to human error” had caused the crash.
“Investigations continue to identify and prosecute this great tragedy and unforgivable mistake,” he said.
“The Islamic Republic of Iran deeply regrets this disastrous mistake.”
Mr Rouhani blamed the tragedy on “threats and bullying” by the US after the killing of Gen Soleimani on January 3 in an American drone.
Ukraine’s president Volodymyr Zelenskiy said his country expected “assurances” from Iran of a “full and open investigation” to bring the perpetrators to justice.
He said Ukraine expected the “paying of compensation” and “official apologies through diplomatic channels”.
Meanwhile Ukrainian International Airlines vice president Ihor Sosnovskiy strongly criticised the Iranian authorities for keeping open their civil airspace in the midst of hostilities with the US.
“When you act in war then you act however you wish. But there must be protection around ordinary people. If they are shooting somewhere from somewhere, they are obliged to close the airport,” he said.