Israeli airstrikes pounded Gaza on Tuesday, killing more than 400 people, according to Palestinian health authorities, in one of the deadliest days since the war began. The bombardment shattered nearly two months of relative calm following a ceasefire, which Israel declared over, warning that the assault was “just the beginning.”

Both Israel and Hamas accused each other of violating the truce, which had been in place since January, offering temporary relief to Gaza’s 2.3 million residents. Hamas, which still holds 59 of the hostages it seized in its October 7, 2023 attack, accused Israel of jeopardizing diplomatic efforts for a permanent peace deal but did not threaten immediate retaliation.

Israeli Prime Minister Benjamin Netanyahu said the strikes were ordered because Hamas rejected proposals to extend the ceasefire.

“From now on, Israel will act against Hamas with increasing force. And from now on, negotiations will only take place under fire,” Netanyahu said in a televised address from the Kirya army base in Tel Aviv.

“Hamas has already felt the blow of our arm in the last 24 hours. And I want to assure you: This is just the beginning.”

The strikes targeted homes and makeshift tent camps across Gaza. Witnesses reported Israeli warplanes firing missiles into Gaza City, while tanks shelled the enclave from across the border. According to Palestinian health authorities, 408 people were killed, many of them children, and 562 others wounded.

“It was a night of hell. It felt like the first days of the war,” said Rabiha Jamal, a 65-year-old Gaza resident.

Families in Beit Hanoun and Khan Younis fled their homes after the Israeli military ordered evacuations from what it labeled “dangerous combat zones.” Many carried their belongings on foot, while others used cars and rickshaws to escape the escalating violence.

The renewed hostilities drew swift condemnation from mediators Egypt and Qatar, while the European Union lamented the collapse of the ceasefire. U.N. emergency relief coordinator Tom Fletcher warned that “modest gains” made during the truce had been wiped out.

Israel has halted aid deliveries to Gaza for more than two weeks, worsening an already dire humanitarian crisis. Hospitals, already struggling after months of bombardment, were overwhelmed by casualties.

Despite the devastation, the U.S. placed full blame on Hamas. Acting U.S. Ambassador to the United Nations Dorothy Shea said Hamas’s refusal to release hostages was responsible for the resumption of fighting. White House National Security Council spokesman Brian Hughes echoed this sentiment, stating, “Hamas could have released hostages to extend the ceasefire but instead chose refusal and war.”

Hamas announced that several of its senior figures were killed in the Israeli airstrikes, including Essam Addalees, head of the Hamas government; Ahmed Al-Hetta, deputy justice minister; and Mahmoud Abu Watfa, head of Hamas-run security services.

Meanwhile, Israeli forces continued operations in the occupied West Bank and launched airstrikes on Hezbollah targets in Lebanon and Syria.

Despite the renewed violence, Hamas spokesman Abdel-Latif Al-Qanoua told Reuters the group remains in touch with mediators and is committed to fulfilling the terms of the original ceasefire agreement. Hamas accused Israel of reneging on the deal by refusing to discuss the next phase of the truce and by blocking humanitarian aid deliveries.

Negotiations in Doha had previously secured the release of 33 Israeli hostages and five Thai nationals in exchange for around 2,000 Palestinian prisoners. Israel had been pushing for an extension of the ceasefire until after the Jewish holiday of Passover and the Muslim fasting month of Ramadan.

The war erupted after Hamas-led gunmen attacked Israel on October 7, 2023, killing about 1,200 people, according to Israeli authorities. Since then, Israeli military operations in Gaza have killed more than 48,000 people, according to Palestinian health officials, reducing much of the territory to rubble.

As the fighting intensifies, the prospect of a lasting peace appears increasingly uncertain.