Israel vowed on Tuesday to continue fighting in Gaza until the return of all hostages as it unleashed its most intense strikes since a ceasefire, with the health ministry in the Hamas-run territory reporting more than 330 people killed.
Hamas accused Israeli Prime Minister Benjamin Netanyahu of deciding to "resume war" after an impasse in truce negotiations, and warned that the return to fighting could be a "death sentence" for hostages still alive in Gaza.
The strikes were by far the biggest and deadliest since a truce took effect on January 19. Hamas has not responded to the strikes so far.
Netanyahu warned Hamas this month of consequences it "cannot imagine" if it does not free hostages still in Gaza, and Israeli media said Israel had drafted plans to ramp up pressure on Hamas under a scheme dubbed the "Hell Plan".
The White House said Israel consulted US President Donald Trump's administration before launching the wave of strikes, which the health ministry in Gaza said killed mostly women and children.
Netanyahu's office said the operation was ordered after "Hamas's repeated refusal to release our hostages, as well as its rejection of all of the proposals it has received from US Presidential Envoy Steve Witkoff and from the mediators".
"Israel will, from now on, act against Hamas with increasing military strength," the statement said.
"We will not stop fighting as long as the hostages are not returned home and all our war aims are not achieved," Defence Minister Israel Katz said.
Apart from the release of the remaining hostages, Israel's other main war aim is to crush Hamas.
In a statement, Hamas said: "Netanyahu and his extremist government have decided to overturn the ceasefire agreement.
"Netanyahu's decision to resume war is a decision to sacrifice the occupation's prisoners and impose a death sentence on them," it said.
A Hamas official said the group was "working with mediators" to stop the strikes, adding that the movement had "adhered to the ceasefire".
In Khan Yunis in the southern Gaza Strip, AFP footage showed people rushing stretchers with wounded people, including young children, to the Nasser Hospital. Bodies covered with white sheets were also taken to the hospital's mortuary.
Mohammed Jarghoun, 36, was sleeping in a tent near his destroyed house in Khan Yunis when he was woken by huge blasts.
"I thought they were dreams and nightmares, but I saw a fire in my relatives' house. More than 20 martyrs and wounded, most of them children and women."
Ramez Alammarin, 25, described carrying children to hospital southeast of Gaza City.
"They unleashed the fire of hell again on Gaza," he said of Israel, adding that "bodies and limbs are on the ground, and the wounded cannot find any doctor to treat them.
"They bombed a building in the area and there are still martyrs and wounded under the rubble... fear and terror. Death is better than life."
Families of Israeli hostages in Gaza pleaded with Netanyahu to "stop the killing and disappearance" of their loved ones, and called for a protest in front of the premier's residence.
Brokered by Qatar, Egypt and the United States, the initial phase of the ceasefire took effect on January 19, largely halting more than 15 months of fighting in Gaza triggered by Hamas's October 7, 2023 attack on Israel.
That first phase ended in early March, and the two sides have been unable to agree on the next steps.
Mohammed Zaqut, head of the health ministry in Hamas-run Gaza, said "at least 330 deaths" had been recorded, "most of them Palestinian women and children".
He said there were "hundreds of wounded, dozens of them in critical condition".
Israel ordered all schools near the Gaza border to shut, amid fear of attack.
US envoy Witkoff told CNN on Sunday he had offered a "bridge proposal" that would see five living hostages, including Israeli-American Edan Alexander, released in return for freeing a "substantial amount of Palestinian prisoners" from Israel jails.
Hamas had said it was ready to free Alexander and the remains of four others.
Witkoff said Hamas had provided "an unacceptable response" and "the opportunity is closing fast".
White House Press Secretary Karoline Leavitt confirmed that Trump's administration had been consulted ahead of Israel's operation.
"As President Trump has made it clear, Hamas, the Huthis, Iran, all those who seek to terrorise not just Israel, but also the United States of America, will see a price to pay -- all hell will break loose," she said.
Yemen's Huthis, part of Iran's "axis of resistance" against Israel and the United States, vowed to escalate its attacks in the Red Sea in solidarity with Hamas.
During the first phase of the truce, Hamas released 33 hostages, including eight deceased, and Israel freed around 1,800 Palestinian detainees.
Since then, Hamas has consistently demanded negotiations for the second phase.
Former US president Joe Biden had outlined a second phase which would involve the release of remaining living hostages, the withdrawal of all Israeli forces left in Gaza and the establishment of a lasting ceasefire.
Israel, however, seeks to extend the first phase until mid-April, insisting any transition to the second phase must include "the total demilitarisation" of Gaza and the removal of Hamas, which has controlled the territory since 2007.
The talks have been deadlocked, and Israel has cut aid and electricity to the territory.
Hamas's October 7, 2023 attack resulted in 1,218 deaths on the Israeli side, mostly civilians, while Israel's retaliatory response in Gaza has killed at least 48,572 people, also mostly civilians, according to figures from the two sides.
Of the 251 hostages seized during the attack, 58 are still held in Gaza, including 34 the Israeli military says are dead.
Both Russia and China warned against an escalation in Gaza.
