Iran's exiled Prince Reza Pahlavi says the Islamic Republic Supreme Leader Ayatollah Ali Khamenei is responsible for the downing of a Ukraine Airlines Boeing, which killed all 176 people onboard.

Three days after the airliner crashed on a flight from Tehran to Kyiv, the Islamic Republic admitted that it was "erroneously" shot down by an anti-aircraft missile.

The last heir apparent to the Iranian throne, 59-year-old Prince Reza, insisted in a tweet on Saturday that shooting down Ukraine's passenger plane was a "crime against humanity," not "human error", as Iran’s government says.

The prince tweeted that the tragedy is the result of an order Khamenei issued in June 2017 to his supporters to "fire at will" against presumed enemies.

However, under a barrage of criticism at the time, he downplayed his comment, saying that he meant that "Iranian Cyber Space Officers" were authorized to freely attack the "enemy" whenever needed.

Nonetheless, close allies of Khamenei have repeatedly referred to his remark, asserting that the Islamic Republic forces were entitled to fire at will.

In his January 11 tweet, Prince Reza lambasted Khamenei, noting that the leader who has ordered firing at will, was directly responsible for the outcome of his decree.

"Enough is enough. Khamenei and his regime must go," Prince Reza tweeted.

In recent anti-Islamic Republic protests across Iran, chants rang out in praise of the last royal family.