Gaza City, Palestinian Territories — Israeli Prime Minister Benjamin Netanyahu warned on Tuesday that massive overnight strikes on Gaza were "only the beginning" and that future negotiations with Hamas "will take place only under fire".

The strikes, by far the largest since a truce took effect in January, killed more than 400 people across the Gaza Strip, according to the health ministry in the Hamas-run territory.

Netanyahu said in a video statement on Tuesday evening "Hamas has already felt the strength of our arm in the past 24 hours. And I want to promise you — and them — this is only the beginning".

Negotiations have stalled over how to proceed with a ceasefire whose first phase has expired, with Israel and Hamas disagreeing on whether to move to a new phase intended to bring the war to an end.

The Israeli premier said in his address that "from now on, negotiations will take place only under fire," before adding: "Military pressure is essential for the release of additional hostages".

Israel has vowed to keep fighting until the return of all the hostages seized by Palestinian militants during the October 2023 attack that sparked the war.

By Tuesday afternoon, witnesses in Gaza said the attacks had largely stopped, though sporadic bombing continued.

"Today I felt that Gaza is a real hell," said Jihan Nahhal, a 43-year-old woman from Gaza City, adding that some of her relatives were wounded or killed in the strikes.

"Suddenly there were huge explosions, as if it were the first day of the war."

Hamas has not responded militarily so far, and in a statement urged friendly countries to "pressure" the United States to bring to an end the strikes by its ally Israel.

Hugh Lovatt, senior policy fellow at the European Council on Foreign Relations, told AFP that "Hamas does not want to be dragged into another war".

The White House said Israel consulted US President Donald Trump's administration before launching the strikes, while Israel said the return to fighting was "fully coordinated" with Washington.

A State Department spokesperson said that "Hamas bears total responsibility... for the resumption of hostilities".

The United Nations and countries around the world condemned the strikes, while the families of Israeli hostages pleaded with Prime Minister Benjamin Netanyahu to halt the violence, fearing for the fate of their loved ones.

'Complete destruction'

Netanyahu's office said Tuesday's operation was ordered after "Hamas's repeated refusal to release our hostages".

Hamas said Israel had "decided to overturn the ceasefire agreement" brokered by US, Qatari and Egyptian mediators, and warned that the resumption of violence would "impose a death sentence" on the remaining living hostages.

The group's leader, Sami Abu Zuhri, told AFP the aim of the strikes was "to impose a surrender agreement, writing it in the blood of Gaza".

Defence Minister Israel Katz said that "Hamas must understand that the rules of the game have changed", threatening to unleash the Israeli military until the group's "complete destruction" if it did not immediately free the hostages.

Hamas said the head of its government in Gaza, Essam al-Dalis, was among several officials killed.

In the southern Gaza Strip, AFP footage showed people rushing wounded people on stretchers, including young children, to hospital. Bodies covered with white shrouds were also taken to the hospital's mortuary.