Gaza: Israel launched an assault on Gaza's biggest city, weeks after pulling back from it, while Washington vowed on Monday to take "all necessary actions" to defend its troops after a deadly attack in Jordan, the first US military deaths in the Middle East since the Gaza war began.

In northern Gaza, residents said air strikes on Monday on neighbourhoods across Gaza City, the enclave's biggest city, killed and wounded many people. While Israeli tanks shelled eastern areas of the city, naval vessels fired at beachfront areas in the west, they said.

Israel said late last year that it had largely completed operations in northern Gaza and has recently aimed the brunt of its might at southern Gaza. The renewed push in Gaza City, where residents reported fierce gun battles near the main Al-Shifa Hospital, suggested that the war was not going to plan.

Among those killed were two Palestinian journalists, Essam El-lulu and Hussein Attalah, and several members of their families, health officials and the journalists' union said.

Hamas, for its part, fired its first volley of rockets for weeks into Israeli cities, proving that the militant group running Gaza still had the capability to launch them after nearly four months of war.

The Israeli military said it shot down six of 15 rockets. There were no reports of any casualties in Israel, where air raid sirens and explosions of interceptions sounded.

Biden pressured to respond to Jordan attack
A day after three US service members in Jordan were killed and at least 34 wounded in what Washington called a drone attack by Iran-backed militants, President Joe Biden's administration was under pressure to respond firmly without triggering a wider war.

"The president and I will not tolerate attacks on US forces and we will take all necessary actions to defend the US and our troops," Defence Secretary Lloyd Austin said on Monday at the Pentagon.

White House National Security spokesman John Kirby said: "We don't want a wider war with Iran. We don't want a wider war in the region, but we got to do what we have to do."

Iran has denied any role. Biden has previously ordered retaliatory attacks on Iran-backed groups but has so far stopped short of hitting Iran directly.

"Have no doubt - we will hold all those responsible to account at a time and in a manner of our choosing," Biden said on Sunday.

Israel is ignoring the world court: Gazans
Meanwhile, Gazans said the violence in the enclave made a mockery of a World Court ruling last week calling on Israel to do more to help civilians. Gaza health officials say 26,637 Palestinians have been killed in the conflict with thousands more bodies likely under the rubble of destroyed buildings.

"The war continues in a dirtier manner," said Gaza City resident and Palestinian human rights activist Mustafa Ibrahim, displaced with his family in Rafah near the southern border with Egypt, along with more than a million other Gazans.

Israel ordered new evacuations of the most populated areas of Gaza City, but people said communications blackouts meant many would miss the alerts. Israel says Hamas is responsible for the deaths of civilians because its fighters operate among them, which the fighters deny.

People in the north have been grinding animal feed to make flour after flour, rice and sugar ran out, part of an aid crisis now potentially exacerbated by a withdrawal of support for the United Nations' aid agency for Palestinian refugees, UNRWA.

The United States and several other countries have suspended aid to the agency since Friday after Israel said 13 of UNRWA's 13,000 staff in Gaza were involved in the October 7 Hamas attacks on Israel, which killed about 1,200 people.

UN Secretary-General Antonio Guterres met the head of UN internal investigations to ensure an inquiry into the allegations "will be done swiftly and as efficiently as possible," a UNspokesperson said.

The Israeli report, seen by Reuters, said 190 UNRWA staff were militants and named 11.

UNRWA, which says more than 150 of its staff have been killed since October and a million Palestinians are sheltering in its buildings, said it would have to end operations within a month if funding was not restored. It said it had promptly fired staff after being alerted to Israel's allegations.

Air strikes on Monday also hit the southern city of Khan Younis, the main focus of Israeli attacks since last week. That has brought fighting deep into territory where hundreds of thousands of people who already fled other areas are sheltering.

Israel's military said on Monday it will keep pressure on the city and that it has killed more than 2,000 Palestinian militants there.

In a renewed, desperate exodus, people went south on foot carrying children and bedding. Suleiman Abusari, a boy in a wheelchair pushed by his father, said his legs were amputated after an Israeli drone hit him.

"My dream was to play football," he said. "They stole my dream."

'Not over the finish line'
Biden and other leaders have been pushing for a new temporary ceasefire to allow for the release of hostages held by Hamas and more aid to reach Gaza.

Talks on Sunday initiated by Qatar and involving US, Israeli and Egyptian intelligence chiefs were "constructive", Israel said, while adding that "significant gaps" remain.

Hamas reiterated on Monday that Israel must halt its Gaza offensive and withdraw from the Gaza Strip before any prisoner exchange takes place. Israel says it will fight until Hamas is eradicated.

The White House's Kirby said negotiations for a new hostage deal had been constructive but much work remains to be done. US Secretary of State Antony Blinken told a news conference the talks had been important and "hopeful."

Kirby also said comments by some Israeli politicians were "reckless" and "incendiary" after Israel's hard-right Security Minister Itamar Ben-Gvir urged Jewish settlers to return to Gaza. Ben-Gvir's remark drew condemnation from Palestinians who said his words amounted to a call for their forced deportation.