Human rights experts commissioned by the United Nations (UN) have concluded that there are "reasonable grounds" to believe that the US committed a war crime when it struck a school in Iran.

An international fact-finding mission said its probe centred on two airstrikes that killed at least 178 civilians, including women and children.

At the start of the US-Israeli war against Iran in February, at least one American missile hit the Shajareh Tayyebeh school in Minab, in the country's south.

Iranian state media has said that 168 people were killed in the strike, most of them children.

"Following the US and Israeli attacks on 28 February, the mission found reasonable grounds to believe the US committed the war crime of launching indiscriminate attacks resulting in the loss of life or injury to civilians or damage to civilian objects," the team said in a statement.

The Trump administration is yet to directly accept responsibility - or release the findings of a Pentagon investigation into the school bombing.

A White House spokesperson on Thursday accused the UN Human Rights Council of accomplishing "nothing for human rights while spouting unserious nonsense for decades".

They added: "The only party in this conflict that has committed war crimes is the Iranian regime, which has murdered thousands of its own people, killed Americans overseas, executed acts of terrorism in the Strait of Hormuz, and launched indiscriminate attacks against its neighbours in the region."

A Sky News investigation heard from seven independent experts that the evidence pointed towards US responsibility.

The experts found there were ample opportunities for US intelligence analysts to identify that the building was a school before launching the strike.

The findings were reported in Sky News documentary, Iran School Bombing: The Search for Truth.

Military insiders also revealed that concerns had been raised for years that the Pentagon was using outdated targeting information, but the warnings were ignored.

The other incident investigated by the UN-backed team was an airstrike in which precision missiles dispersed tungsten pellets over a "clearly identifiable sports complex and residential area" in the southern city of Lamerd.

The fact-finding team said 22 civilian men and women were killed in the strike that also took place on 28 February.

US Central Command has denied responsibility for the strike.

The team also said that killings by state security forces occurred on a "staggering scale" in Iran, and alleged that crimes against humanity were committed by the Iranian government.

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Civilians were caught between "gross human rights violations and crimes against humanity committed by their own government and the nation's deadly conflict with the United States and Israel", the team added.

The mission, chaired by jurist Sara Hossain of Bangladesh, is made up of independent experts, and was created in 2022 by the Human Rights Council, the UN's top human rights body.