220 reported dead as Israel pounds Gaza in most intense strikes since ceasefire
The White House confirmed that Israel consulted US President Donald Trump's administration before launching the wave of strikes, which rescuers said killed mostly women, children and elderly.
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," said the statement.
An Israeli official told AFP the military operation would "continue as long as necessary" and was expected to "expand beyond air strikes".
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, accusing the Israeli prime minister of using the conflict as a political "lifeboat" to stay afloat amid domestic crises.
AFP footage showed people rushing stretchers with injured people, including young children, to the Nasser hospital in Khan Yunis. 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 twenty 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."
'Hell will break loose'
Mediated 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' October 7, 2023 attack on Israel.
That first phase ended in early March, and while both sides have since refrained from all-out war, they have been unable to agree on the next steps for truce talks.
Israel has also been carrying out near-daily strikes on Gaza, but not on the scale of Tuesday's operation.
In a post on Telegram in the early hours of Tuesday, the Israeli army said it was "conducting extensive strikes on terror targets belonging to the Hamas terrorist organisation in the Gaza Strip".
Gaza's civil defence agency reported more than 220 people killed, "most of them children, women and the elderly". At least 150 people were also wounded by the "aggression, aerial bombardment and artillery shelling".
Israel ordered all schools close to the regions neighbouring Gaza shut, as the government said it would ramp up military action against Hamas.
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 Tuesday 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 in the televised interview.
Deadlock
During the first phase of the truce agreement, 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 involving 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 stuck at an impasse, and Israel has cut aid and electricity to the territory during the deadlock.
"It's so hard for me to think about what they're (hostages) going through right now because I know that feeling," freed Israeli captive Omer Shem Tov said in a recently released video.
"It's a terrible feeling and it has to stop as soon as possible."
Hamas' October 7 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 data from both sides.