The Iranian military said it mistook the Ukrainian International Airlines Flight 752 as a "hostile target," following reports of missiles heading towards Iran.

The passenger plane bound for Kyiv, Ukraine, was taken down by an Iranian missile shortly after taking off from Tehran on Wednesday. The crash killed all 176 passengers on board.

Iran admitted on Saturday morning local time to accidentally downing the jet, blaming "human error."

Iran initially denied responsibility and blamed the crash on a mechanical problem with the jet, a Boeing 737-800.

The Iranian Armed Forces released a statement, further explaining the "error," saying that the Ukrainian jet approached a "sensitive military site of the [Islamic Revolutionary Guard Corps], taking the shape and altitude of a hostile target," according to Sky News' Mark Stone.

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The Iranian military said it mistook the Ukrainian International Airlines Flight 752 as a "hostile target," with a senior commander saying the country's security officials believed the plane was a missile.

The passenger plane bound for Kyiv, Ukraine, was downed by an Iranian missile shortly after taking off from Tehran on Wednesday. The crash killed all 176 passengers on board.

Brig-Gen Amir Ali Hajizadeh, the aerospace chief for Iran's Revolutionary Guard, said on Saturday that defences had been put on "full alert" after reports that "cruise missiles had been fired at the country."

"The unit faced a target in a distance of 19km which it presumed to be a cruise missile," he said.

On Saturday morning local time, Iran admitted to accidentally firing at the jet, blaming "human error." Iran initially denied responsibility and blaming the crash on a mechanical problem with the jet, a Boeing 737-800.

The Iranian Armed Forces released a statement, saying that the Ukrainian jet approached a "sensitive military site of the [Islamic Revolutionary Guard Corps], taking the shape and altitude of a hostile target," according to Sky News' Mark Stone.

Iranian President Hassan Rouhani also released a statement, translated by the BBC, citing "an atmosphere of threats and intimidation by the aggressive American regime against the Iranian nationa following the martyrdom of general Qassem Soleimani and with the aim of defending against possible US Army attacks, the Islamic Republic of Iran's Armed forces were on full alert," when the plane was shot down.

The timing of the incident, came after Iranian defense units received reports of "flying targets moving towards Iran's strategic centers," at a time when reports of "military flights of the US' terrorist forces had increased around the country," the Iranian military said.

"In such conditions, due to human error and in an unintentional move, the airplane was hit, which caused the martyrdom of a number of our compatriots and the deaths of several foreign nationals," the statement said.

Rouhani said on Saturday that investigations will continue "to identify and prosecute this great tragedy and unforgivable mistake."

"The Islamic Republic of Iran deeply regrets this disastrous mistake," Rouhani continued. "My thoughts and prayers go to all the mourning families. I offer my sincerest condolences."

The plane was downed shortly after Iran launched more than a dozen missiles at US troops stationed in Iraq. No casualties emerged from the missile attack on two Iraqi military bases where US and coalition forces were housed. That strike was in retaliation for the death of Iran's most prominent military commander, Maj. Gen. Qassem Soleimani, who was killed last week by a drone strike ordered by US President Donald Trump.