Israel has issued a new evacuation order for southern Gaza's Khan Younis a day after killing nearly 100 Palestinians in an airstrike on a school.

Tens of thousands of Gazan residents and displaced families were forced to leave in the dark as explosions from tank shelling reverberated around them.

The Israeli military claimed it was attacking the Hamas group – which administered Gaza before the war – who were using those areas to stage attacks and fire rockets.

On Saturday, an Israeli airstrike on a school where displaced Palestinians were sheltering in Gaza City killed at least 93 people, according to the civil defense service, prompting an international outcry.

The bombardment of the al-Tabieen religious school and mosque drew criticism from across the Middle East and beyond alongside calls for a cease-fire after international mediators invited the warring sides to resume talks towards a long-sought truce and hostage-release deal.

Civil defense rescuers said three Israeli missiles hit the complex in Gaza City while people were performing dawn prayers. The military confirmed it had used "three precise munitions."

Mahmud Bassal, a spokesperson for the civil defense agency, said 11 children and six women were among the 93 who died at the school shelter, "and there are many unidentified body parts."

Hamas denounced it as a "dangerous escalation," while the Palestinian group's Lebanese ally Hezbollah called it a "horrific massacre."

Iran, which backs both groups and had accused Israel of wanting to spread war in the Middle East following high-profile killings in Tehran and Beirut, condemned what it called a "barbaric attack."

The Israeli military said it had struck a Hamas and Islamic Jihad installation, an allegation the two groups rejected.

International outcry

Jordan's Foreign Ministry said the timing was an indication of Israel's efforts to "obstruct and thwart" the latest mediation effort.

One of the mediators, Qatar, called for an "urgent international investigation," while Türkiye said Israeli Prime Minister Benjamin Netanyahu wanted "to sabotage ceasefire negotiations."

The European Union's foreign policy chief Josep Borrell said the school strike left him "horrified".

France said "Israel must respect international humanitarian law."

"For several weeks, school buildings have been repeatedly targeted, with an intolerable number of civilian victims," the French Foreign Ministry said.

Nowhere to go

With nearly all of the Gaza Strip's 2.4 million people displaced at least once during the war, many have sought refuge in school buildings, which have been hit at least 14 times since July 6, according to an AFP tally.

In Khan Younis in the south of the Gaza Strip, the evacuation instruction covered districts in the center, east and west, making it one of the largest such orders in the 10-month-old conflict, two days after tanks returned to the east of the city.

The announcement was posted on X and in text and audio messages to residents' phones: "For your own safety, you must evacuate immediately to the newly created humanitarian zone. The area you are in is considered a dangerous combat zone."

Philippe Lazzarini, head of the United Nations agency for Palestinian refugees (UNRWA), said people in Gaza were trapped and had nowhere to go.

"Some are only able to carry their children with them, some carry their whole lives in one small bag. They are going to overcrowded places where shelters are already overflowing with families. They have lost everything and need everything," he said.

The Israeli army said it had struck around 30 Hamas targets in the previous 24 hours, including military structures.

The Islamic Jihad said fighters fired mortar bombs against Israeli forces massing in the eastern areas of Khan Younis.

Later Sunday, an Israeli airstrike near the Khan Younis market at the center of the city killed four Palestinians and wounded several others, medics said.

Lines of smoke rose from areas where Israeli planes carried attacks in the eastern and western parts of the city. Residents said two multi-floor buildings were bombed.

Nearly 40,000 Palestinians have been killed in the Israeli offensive in Gaza since the war broke out last October and the toll is rising by the day, the Gaza Health Ministry says.

Israel began its genocidal war on Gaza after the Oct. 7 Hamas incursion killed 1,200 people and captured more than 250 hostages, according to Israeli tallies.