The United States has said Israel must make every possible effort to avoid civilian casualties, following a deadly strike that hit a displacement camp in Rafah.
Israel is facing a wave of international condemnation over the strike, both across the region and from the European Union, France and the United Nations.
"As we've been clear, Israel must take every precaution possible to protect civilians," a US National Security Council spokesperson said in a statement.
"We are actively engaging the IDF and partners on the ground to assess what happened," the spokesperson added.
Gaza's civil defence agency said the strike ignited a fire that tore through a displacement center in northwestern Rafah near a facility of the UN agency for Palestinian refugees.
"The devastating images following an IDF strike in Rafah last night that killed dozens of innocent Palestinians are heartbreaking," the US spokesperson said.
The Israeli military said it had launched a probe into the strike which it said was carried out based on "precise intelligence information" about two Hamas militants who it said were killed.
It launched the attack on Rafah hours after Hamas unleashed a barrage of rockets towards the Tel Aviv area, most of which were intercepted.
The US spokesperson said that "Israel has a right to go after Hamas, and we understand this strike killed two senior Hamas terrorists who are responsible for attacks against Israeli civilians," before imploring more caution.
Mediator nation Qatar has said the strikes could hinder talks towards a truce and hostage release deal.
Israel's army said its aircraft "struck a Hamas compound in Rafah", killing two senior officials for the Palestinian militant group in the West Bank.
Qatar's foreign ministry voiced "concern that the bombing will complicate ongoing mediation efforts and hinder reaching an agreement for an immediate and permanent ceasefire".
Qatar, alongside the United States and Egypt, has been engaged in months of talks aimed at securing a truce deal between Israel and Hamas in Gaza.
But behind-the-scenes negotiations reached a stalemate earlier this month as Israel sent ground forces into Rafah.
Qatar, which has hosted Hamas's political leadership since 2012 with the blessing of the United States, condemned the Israeli bombing as a "dangerous violation of international law".
The foreign ministry called on the international community to act urgently to prevent Israel from "implementing its plans to forcibly displace (Palestinians) from the city, which has become a final refuge for hundreds of thousands" of people.
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French President Emmanuel Macron said he was "outraged" over Israel's latest attacks. "These operations must stop. There are no safe areas in Rafah for Palestinian civilians," he said on X.
Germany's foreign minister Annalena Baerbock and the EU foreign policy chief Josep Borrell said the International Court of Justice ruling must be respected. "International humanitarian law applies for all, also for Israel's conduct of the war," Ms Baerbock said.
Speaking in Brussels, Tánaiste Micheál Martin described the attack as barbaric and said UN agencies had predicted that Israel's assault on Rafah would have dire consequences.
Kuwait's foreign ministry also decried the Israeli attack on the camp housing displaced Palestinians near Rafah, saying the it exposed Israel's "blatant war crimes and unprecedented genocide to the whole world".
The Gulf monarchy called for "immediate and firm intervention by the international community".
Egypt condemned what it called the "deliberate bombardment by Israeli forces of displaced peoples' tents".
The Egyptian Foreign Ministry issued a statement calling on Israel to "implement the measures ordered by the International Court of Justice (ICJ) concerning an immediate cessation of military operations" in Rafah.
The ministry condemned the strike as "a new flagrant violation of the provisions of international humanitarian law".
It deplored the "tragic event" and denounced the "targeting of defenceless civilians" and "a systematic policy aimed at widening the scope of death and destruction in the Gaza Strip to make it uninhabitable".
Jordan also expressed its condemnation, accusing Israel of committing "ongoing war crimes".
Amman said the bombardment in Rafah "defies the rulings of the International Court of Justice and constitutes a severe violation of international law and international humanitarian law".
