Boris Johnson has said that Iran admitting it had accidentally shot down an Ukrainian airliner was "an important first step" but said Tehran must now cooperate with international investigators.

“Iran’s admission that Ukraine International Airlines Flight 752 was shot down by mistake by its own armed forces is an important first step," the prime minister said.

“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 Queen also sent a message of condolence to the governor-general of Canada, saying she and Prince Phillip were "deeply saddened by the tragic loss of life".

Iran’s supreme leader claimed he was only told on Friday that his forces shot down the airliner and therefore was not responsible for days of false denials that Iran was not involved in the disaster.

The Iranian military admitted it “unintentionally” destroyed the airliner, killing all 176 people aboard, and said air defence operators mistook the civilian aircraft for an incoming American cruise missile.