In a video address to the United Nations Human Rights Council, Abbas Araghchi slammed the "calculated, phased assault" on an elementary school "in the city of Minab, south of Iran, where more than 175 students and teachers were slaughtered in cold blood".

The attack happened on February 28, the day the United States and Israel launched the war with attacks across Iran, with Tehran in turn striking targets in Israel and Gulf nations.

A US Tomahawk cruise missile hit the school due to a targeting mistake, according to the preliminary findings of a US military investigation reported by The New York Times.

The Times said the US military was bombing an adjacent Iranian base of which the school building was formerly a part and target coordinates were set using outdated data.

President Donald Trump intially suggested that Iran itself may have been responsible -- despite Iran not having Tomahawk missiles.

Speaking during an urgent council debate focused on the February 28 strike, Araghchi stressed that "at a time when the American-Israeli aggressors, in their own assertions, possess the most advanced technologies, and the highest-precision military and data systems, no one can believe that the attack on the school was anything other than deliberate and intentional".

The strike, he said, "was a war crime and a crime against humanity, one that demands unequivocal condemnation by all and unambiguous accountability for the culprits".

"This atrocity cannot be justified, cannot be concealed, and must not be met with silence and indifference," the minister said.

The attack, he insisted, "was not a mere 'incident' nor a 'miscalculation'."

"The United States' contradictory remarks aimed at justifying their crime could not, in any manner, elude their responsibility," he said.