At least 413 Palestinians, including women and children, were killed after the Israeli military conducted "extensive strikes" on Hamas, ending a weeks-long deadlock over extending the ceasefire that paused fighting in January.
Prime Minister Benjamin Netanyahu ordered the strikes after Hamas refused Israeli demands to change the ceasefire agreement.
"Israel will, from now on, act against Hamas with increasing military strength," Netanyahu's office said.
The Israeli military ordered people to evacuate eastern Gaza, including much of the northern town of Beit Hanoun and other communities further south, and head toward the centre of the territory, indicating that Israel could soon launch renewed ground operations.
“Israel will, from now on, act against Hamas with increasing military strength,” Netanyahu's office said.
The White House said the United States had been consulted about the attack and voiced support for Israel's actions.
White House press secretary Karoline Leavitt said that the "Trump administration and the White House were consulted by the Israelis on their attacks in Gaza."
"As President Trump has made it clear, Hamas, the Houthis, Iran all those who seek to terrorize not just Israel, but also the United States of America, will see a price to pay: All hell will break lose," Leavitt told Fox News.
The surprise attack shattered a period of relative calm during the Muslim holy month of Ramadan and raised the prospect of a full return to fighting in a 17-month war that has killed over 48,000 Palestinians and caused widespread destruction across Gaza.
It also raised questions about the fate of the roughly two dozen Israeli hostages held by Hamas who are believed to still be alive.