At least 22 Palestinians were killed and 100 wounded in a strike on Sunday on a UN-run school in central Gaza being used as a shelter by displaced people, said BBC quoting Hamas-run health ministry.
The Israeli military said it had targeted a number of Hamas “terrorists” operating from Abu Oraiban School in the urban Nuseirat refugee camp.
Witnesses told BBC Arabic there were no armed fighters there and that children were among the casualties.
It was the fifth attack on or near to schools in eight days.
Residents said there were fresh air and artillery strikes in central Gaza on Monday, with five people reportedly killed when a house in Maghazi refugee camp was hit. The Israeli military said its aircraft had struck dozens of “terror targets” across the territory over the past day.
Meanwhile, Hamas said indirect negotiations on a ceasefire and hostage release deal with Israel were “ongoing” in the wake of an air strike in the southern al-Mawasi humanitarian area on Saturday that the health ministry said killed more than 90 people.
The Israeli military said it had targeted a compound where the head of Hamas’s armed wing, Mohammed Deif, was hiding with the commander of its Khan Younis Brigade, Rafa Salama.
The military has announced that Salama was killed, but said it is too early to conclude whether Deif also died. Hamas has said Deif is in good health.
A US State Department spokesman said Antony Blinken expressed serious concerns about the recent civilian casualties during a meeting with two key Israeli officials on Monday.
The US Secretary of State spoke with with national security advisor, Tzachi Hanegbi, and Minister of Strategic Affairs, Ron Dermer, who confirmed that Israel was still committed to reaching a ceasefire deal under terms laid out by Joe Biden in May.
Israel launched a military campaign in Gaza to destroy Hamas in response to an unprecedented attack on southern Israel on 7 October, during which about 1,200 people were killed and 251 others were taken hostage.
More than 38,660 people have been killed in Gaza since then, according to the territory’s health ministry, whose figures do not differentiate between civilians and combatants.
Witnesses denied that armed fighters were using Abu Oraiban School as a hideout
According to the UN, an estimated 1.9 million people - 90% of Gaza’s population - have been forced to flee their homes, including some who have been displaced up to 10 times.
Thousands were reportedly sheltering at Abu Oraiban School, which is run by the UN agency for Palestinian refugees (Unrwa), when it was it struck on Sunday afternoon.
A displaced woman told BBC Arabic that she had been lighting a fire to cook in a corridor when a nearby room was hit.
“As soon as the explosion occurred the walls of the room collapsed on us,” she said. “I saw a little boy whose leg was bleeding and a dismembered corpse which people covered with blankets. I also saw a little boy lying in a pool of blood, with his whole face bleeding.”
She added: “I quickly ran out of the school. I found my aunt at the school gate, hugging her burnt young son. When I left the school, I saw many injured people lying on the ground and bodies torn to pieces.”
Another resident said his family had been living at the school for six months because UN facilities were supposed to be safe.
“There are no armed men and no reason to strike schools this way,” he added. “The dead and injured people are mainly women and children staying at this school.”
Video footage filmed by a freelance cameraman working for BBC Arabic later on Sunday showed hundreds of people walking past the rubble of a destroyed structure in one corner of the school compound. A heavily damaged staircase could also be seen through two large holes in a wall of the adjoining three-storey school building.
The Israel Defense Forces (IDF) said Hamas fighters had used the school as “a hideout and operational infrastructure” from which attacks against its troops were directed and carried out.
“Prior to the strike, numerous steps were taken in order to mitigate the risk of harming civilians, including the use of precise munitions and additional intelligence,” it added.
The IDF also accused Hamas of systematically violating international law by exploiting civilians and civilian structures as “human shields” - an accusation the group has denied.
A spokesman for Gaza’s Hamas-run Civil Defence force, told AFP news agency on Sunday evening that 15 people were killed and that most were women and children.
On Monday, the health ministry said the death toll had risen to 22, but it did not provide any further details.
Hamas condemned the Israeli strike as what it called an “extension of the genocide” against displaced Palestinians.
The IDF has acknowledged carrying out five strikes on or near to schools sheltering displaced people since 6 July. It has said they targeted Hamas politicians, police officers and fighters using them as bases.
Last Tuesday, hospital officials said at least 29 people had been killed in an Israeli strike on a camp for displaced people outside a school in the town of Abasan al-Kabira, near the southern city of Khan Younis.
A total of 20 people, including a senior Hamas government official, were reportedly killed in three earlier strikes at two other Unrwa-run schools in Nuseirat and a church-run school in Gaza City.