The international fact-finding mission on Iran says the findings center on a pair of airstrikes that killed at least 178 civilians, including women and children.
At the start of the US-Israeli war of aggression against Iran in February, a US munition hit the Shajareh Tayyebeh school in Minab, NBC News reported.
There has been no final accounting of what happened. Iranian state media have said 168 people were killed in the strike, most of them children.
“Following the United States and Israeli attacks on February 28, the mission found reasonable grounds to believe the United States committed the war crime of launching indiscriminate attacks resulting in the loss of life or injury to civilians or damage to civilian objects,” the fact-finding team said in a statement.
The Trump administration has yet to directly accept the blame or release findings of a Pentagon investigation into the school bombing.
The UN-backed team cited the allegations of war crimes over two strikes — one involving Tomahawk missiles on the “clearly identifiable” school, and another airstrike where precision strike missiles dispersed tungsten pellets over a “clearly identifiable sports complex and residential area” in the southern city of Lamerd, also on Feb. 28.
The UN-backed team said 22 civilian men and women were killed. US Central Command has denied responsibility for the strike on Lamerd.