Strikes on Gaza Strip just the beginning: Netanyahu

Israeli air strikes have pounded the Gaza Strip and killed more than 400 people, Palestinian health authorities say, in an onslaught across the enclave that ended weeks of relative calm after talks to secure a permanent ceasefire stalled.

Israel and Palestinian militant group Hamas each accused the other of breaching the truce, which had broadly held since January, offering respite from war for the two million inhabitants of the Gaza Strip, where most buildings have been reduced to rubble.

Hamas, which still holds 59 of the 250 or so hostages Israel says the group seized in its October 7, 2023 attack, accused Israel of jeopardising efforts by mediators to negotiate a permanent deal to end the fighting but the group made no threat of retaliation.

Israeli Prime Minister Benjamin Netanyahu on Tuesday defended the resumption of air strikes, saying that negotiations on restoring the ceasefire would continue "only under fire".

In a briefing, Netanyahu said military pressure on Hamas was a "critical condition" for securing the release of hostages held by the militant Islamist group, adding: "This is just the beginning".

Netanyahu earlier said he ordered strikes because Hamas had rejected proposals to secure a ceasefire extension during faltering talks.

"Israel will, from now on, act against Hamas with increasing military strength," the prime minister's office said in a statement.

The strikes hit houses and tent encampments from the north to the south of the Gaza Strip, and Israeli tanks shelled from across the border line, witnesses said.

The Hamas-run health ministry in the enclave said 404 people had been killed in one of the biggest single-day tolls since the war erupted.

"It was a night of hell. It felt like the first days of the war," said Rabiha Jamal, 65, a mother of five from Gaza City, who said her building shook as the explosions began.

Families in Beit Hanoun in the northern Gaza Strip and eastern areas of Khan Younis in the south fled their homes, some on foot, others in cars or rickshaws, carrying some of their belongings after the Israeli military issued evacuation orders warning the areas were "dangerous combat zones".

Egypt and Qatar, mediators in the ceasefire deal along with the United States, condemned the Israeli assault.

The United Nations emergency relief co-ordinator Tom Fletcher said the "modest gains" made during the ceasefire had been destroyed.

He said humanitarian aid and commercial essentials must be allowed to enter the Gaza Strip.

Israel has halted aid deliveries into the enclave for more than two weeks, exacerbating a humanitarian crisis.

But Dorothy Shea, acting US ambassador to the UN, said the blame for the resumption of Gaza Strip hostilities "lies solely with Hamas" and expressed support for Israel in its next steps.

Negotiating teams from Israel and Hamas had been in Doha as mediators sought to bridge the gap between the two sides after the end of an initial phase in the ceasefire, during which 33 Israeli hostages and five Thai citizens were released in exchange for about 2000 Palestinian prisoners.

Israel had been pressing for the return of the remaining hostages in exchange for a truce until after the Muslim fasting month of Ramadan and the Jewish Passover holiday in April.

However, Hamas has insisted on moving to negotiations for a permanent end to the war and a full withdrawal of Israeli forces, under the terms of the original ceasefire agreement.

On Tuesday, Hamas spokesman Abdel-Latif al-Qanoua told Reuters the group was still in touch with mediators, and it was keen to complete the implementation of the original deal.

Egyptian mediators were engaged in intense contacts to salvage the ceasefire, two Egyptian security sources said.

Much of Gaza Strip lies in ruins after the war, which erupted on October 7, 2023 when Hamas-led gunmen attacked Israel, killing 1200 people, according to Israeli tallies.

The Israeli campaign in the Gaza Strip has killed more than 48,000 people, Palestinian health authorities say, and destroyed much of the housing and infrastructure in the enclave.