CAIRO - Israel expanded evacuation orders in Khan Younis in the southern Gaza Strip overnight, forcing tens of thousands of Palestinian residents and displaced families to leave in the dark as explosions from tank shelling reverberated around them.

The Israeli military said it was attacking militants from 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 around 100 people, according to the civil defense service, prompting an international outcry.

The Israeli military said it had struck a Hamas and Islamic Jihad militant command post, an allegation the two groups rejected as a pretext, and killed 19 militants.

ALSO READ: Israel strike on Gaza shelter kills around 100, says Hamas media office

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."

The Israeli army said it had struck around 30 Hamas military targets in the previous 24 hours, including military structures, anti-tank missile launch posts and weapons storage facilities.

Tens of thousands forced to leave overnight

Most of Gaza's 2.3 million people have been displaced from their homes, according to the United Nations, while their narrow strip of land has largely been reduced to a wasteland of rubble.

Palestinian and United Nations officials say there are no safe areas in the enclave. Areas designated as humanitarian zones, like Al-Mawasi in western Khan Younis where residents were being sent, have been bombed several times by Israeli forces.

Tens of thousands left their homes and shelters in the middle of the night, heading west toward Mawasi and north toward Deir Al-Balah, already overcrowded with hundreds of thousands of displaced people.

"We're exhausted. This is the 10th time I and my family have had to leave our shelter," said Zaki Mohammad, 28, who lives in the Hamad housing project in western Khan Younis, where the occupants of two multi-floor buildings were ordered to leave.

"People are carrying their belongings, their children, their hopes and their fears and running towards the unknown, because there is no safe place," he told Reuters via a chat app. "We are running from death to death."

International condemnation

Countries in the Middle East on Saturday strongly condemned the deadly Israeli airstrikes launched earlier in the day that targeted the Al-Taba'een School in the Al-Daraj neighborhood in central Gaza City while displaced people in the school were performing morning prayers.

ALSO READ: Israel strike on Gaza shelter kills around 100, says Hamas media office

In a statement released Saturday, Arab League Secretary-General Ahmed Aboul-Gheit said killing displaced civilians during dawn prayers is a crime that "surpasses the usual low level of vileness and unscrupulousness of the Israeli army."

He called on the international community to exert real pressure on Israel to negotiate seriously for an immediate ceasefire in Gaza and a prisoner swap deal.

The Egyptian Foreign Ministry said in a statement on Saturday that Israel's deliberate killing of so many unarmed civilians, whenever mediators intensified efforts to reach a ceasefire in Gaza, is "conclusive evidence of the absence of political will on the part of the Israeli side to end this fierce war."

On Friday, Egypt, Qatar and the United States, three mediators in the current Israel-Hamas conflict, issued a joint statement urging both parties to resume talks in Cairo or Doha on Aug 15 and finalize a ceasefire agreement at an early date.

Qatar's Foreign Ministry also strongly condemned the Israeli bombing of the school, calling for the dispatch of independent UN investigators to probe the ongoing targeting by Israeli forces of schools and shelters for displaced people.

Also on Saturday, the Lebanese Ministry of Foreign Affairs and Emigrants called the "systematic indiscriminate shelling by the Israeli occupation army and the killing of children and civilians" in Gaza "clear evidence of the Israeli government's disregard for the provisions of international law and international humanitarian law."

"The continued crimes against the Palestinians, and the deliberate killing of these huge numbers of civilians, provide conclusive evidence of Israel's intention to prolong the war and expand its scope," the ministry said in a statement, calling on the international community and the concerned parties to "take a unified, serious, and effective international position."

Jordan's Foreign Ministry also condemned the Israeli attacks on the Gaza school, calling the attacks a blatant violation of international law, and a continuation of Israel's systematic targeting of civilians and displacement shelters.

ALSO READ: Israel kills 40 Palestinians in Gaza airstrikes amid fears of wider war

In a statement, the ministry's spokesperson Sufian Qudah said the attacks indicate the Israeli government's intention to obstruct and thwart efforts by the mediators to resume negotiations on a deal leading to a permanent ceasefire.

Qudah urged the international community, particularly the UN Security Council (UNSC), to take the responsibility to immediately stop the Israeli aggression on Gaza, halt the continuous Israeli violations of international law, and hold those behind the attacks accountable.

In a statement, the Iraqi Foreign Ministry strongly condemned the "barbaric" Israeli attacks on the Gaza school, saying Israel's repeated attacks that led to the mass killing of civilians constitute a "flagrant violation" of all international norms and conventions and show the country's disregard for international initiatives aimed at stopping the aggression on Gaza.

Calling Israel's attacks on the Gaza school a "heinous massacre," the Syrian Foreign Ministry said in a statement that Israel's continuous actions for over 10 months constitute crimes of genocide, and are unstoppable due to protection from the West.

ALSO READ: 2 killed in Israeli airstrike on Lebanese town

"Syria ... reaffirms that the Israeli regime's continued bloodshed of innocents in Palestine, Lebanon, and Syria will only strengthen the resolve of the people in this region to resist and retaliate against its crimes, despite the extensive Western support it receives," the statement said, reaffirming Syria's unwavering support for the Palestinian cause and their legitimate rights.

Iranian Foreign Ministry spokesman Nasser Kanaani described the attacks on the Gaza school as "brutal," a clear instance of Israel's simultaneous perpetration of "genocide, war crimes, and crimes against humanity," and a flagrant instance of a threat against global peace and security.

The attacks once again proved that Israel is not committed to any international laws and regulations as well as moral and humanitarian principles, Kanaani said, calling on regional countries to take "decisive and firm" actions to support the Palestinians and on the UNSC to take immediate and effective actions against Israel's behaviors based on the UN Charter.

Israel has been launching a large-scale offensive against Hamas in the Gaza Strip to retaliate against a Hamas rampage through the southern Israeli border on Oct 7, 2023, during which about 1,200 people were killed and about 250 were taken hostage.

READ MORE: UN: Hostilities, continuing displacements challenge Gazans' access to aid

The Palestinian death toll from ongoing Israeli attacks on the Gaza Strip has risen to 39,790, Gaza-based health authorities said in a statement on Saturday.