Four-year-old Mahmoud Abdel Athim al-Saafin wakes up screaming from pain caused by burns suffered in an Israeli strike on a school where his family had been sheltering in the Gaza Strip, his father Abdel Athim al-Saafin said.His two-year-old sister, Maysar, was killed in the July 14 strike in Nuseirat refugee camp, Saafin said. Her body was so badly burned it resembled "a lump of coal", he said.Both sides of Mahmoud's face were burnt, the skin raw and pink from his scalp down to his neck. Both of legs and one of his arms were entirely bandaged, as he lay in a bed in a crowded hospital ward, where Reuters saw him fitfully sleeping.The boy later sat up in bed against a pink pillow, visibly in pain as his father fanned air across his wounds with a piece of a cardboard box.Saafin said the pain-killers being given to Mahmoud lasted a few hours before wearing off. "Then we beg to get an injection, a sedative or painkiller or sleeping (medication) so the child can sleep," he said.Describing the July 14 attack, Saafin said he had been helping children who had been burnt by a first missile strike when a second strike caused "massive destruction"."When we began to pull our children out from under the rubble, we found them all burnt," he said.Little Mahmoud saw the body of his sister. "'My sister is burnt, father’" Saafin recalled the boy saying.Gaza health officials say 17 people were killed and 80 wounded in the July 14 Israeli airstrike on the Abu Oreiban school, sheltering displaced people in Nuseirat in central Gaza. The school is run by UNRWA, the UN agency for Palestinian refugees.The Israeli military declined to comment on the father's remarks. It has said it launched the strike to target fighters who were operating in the area of the school, and took precautions including using precise munitions to reduce civilian casualties. Israel says Hamas fighters are to blame for harm to civilians for operating among them, which the fighters deny.UNRWA Commissioner-General Philippe Lazzarini said in a July 17 statement on X that at least eight schools had been hit in the Gaza Strip in the preceding 10 days, six of them UNRWA schools.Schools must never be used for fighting or military purposes by any party to the conflict, he added."All rules of war have been broken" in Gaza, he wrote.Israel has laid to waste much of Gaza since Hamas stormed southern Israel in the first week of October last year.The death toll among Palestinians in Israel's retaliatory offensive has reached more than 39,000, according to Gaza health authorities.