Tehran has accused the United States and Israel of conducting the deadly missile attack on the school in Iran's south on the first day of the war.

Iranian media reports said funerals were held for at least 165 people, including children, killed in the strike.

The toll has not been verified independently. A US military investigation into the strike is underway.

Beijing's foreign ministry said the Chinese Red Cross Society will donate $200,000 in emergency humanitarian assistance to the Iranian Red Crescent Society, specifically for "condolences and compensations" to the parents of dead students.

Ministry spokesman Guo Jiakun called the strike a "severe violation" of international humanitarian law.

"Attacks on schools and children constitute a more severe violation of international humanitarian law and breach the bottom line of human conscience and morality," Guo told reporters at a regular news briefing.

"China stands ready to continue providing necessary assistance to Iran in a humanitarian spirit to support the Iranian people through this difficult time," he said.

The New York Times reported on Wednesday that the US military investigation has determined that a US Tomahawk missile had struck the school because of a targeting mistake.

Israel has denied any involvement in or knowledge of the strike.

AFP has been unable to access the location to independently verify the circumstances of te strike or the toll.

US President Donald Trump initially suggested that Iran itself may have been responsible, even though Iran does not have Tomahawk missiles.

He said later he could "live with" whatever the investigation reveals but, when asked about the Times report on Wednesday, he told reporters: "I don't know about it."