Iran had denied accusations it was responsible for the plane crash, but has come under intense international pressure over evidence released by Western intelligence services.

The crash of the Ukraine International Airlines Boeing 737-800 occurred hours after Iran launched missiles at two air bases housing US troops in Iraq.

The attacks came in response to the killing of Iranian military commander Qasem Soleimani in a U.S. drone operation in Baghdad on January 3.

On Saturday morning, a military statement was read on Iranian state television announcing that flight PS752 had been mistakenly hit by a missile.

Due to tensions between the United States and Iran, the document said, the military was at the “highest level of readiness.” “In this context, due to human error and without intention, the plane was hit.”

The military apologized, said it would change the security system to prevent further “mistakes” in the future, and announced that those responsible would be tried and punished.

President Rouhani offered his condolences. “(Iran) deeply regrets this disastrous mistake,” he wrote on Twitter.

The country’s foreign minister, Javad Zarif, apologized to the victims’ families but also held the United States responsible. “Human error in a time of crisis caused by the adventurous action of the United States led to disaster,” he said.

For Lyse Doucet, the BBC’s chief international correspondent, Iran’s admission of guilt represents a de-escalation of tensions with the United States.

“Iran has decided that it must acknowledge the disaster to avoid a new war of words with the West or to arouse the fury of its own people, who jump from one calamity to another,” Doucet wrote.

The big question now, she said, is: “Who made the decision to allow a civilian plane to take off when Iranian airspace was under such tension?”

Canadian Prime Minister Justin Trudeau called the plane crash a “national tragedy” – the country is home to nearly 210,000 people of Iranian descent.

In a statement, he called for “transparency and justice for the victims’ families.” A total of 57 Canadians died in the tragedy.

Ukrainian President Volodymyr Zelensky called on Iran to punish those responsible. “We hope that Iran will bring them to justice,” he said.

Ukraine declared a day of national mourning on Thursday over the accident.

Boeing said it was “ready to assist in any way necessary,” while Canadian Prime Minister Justin Trudeau said his country looked forward to participating in the investigation and offered technical assistance.