Six United Nations' agencies have called for an urgent renewal of the ceasefire in Gaza, saying there is an "utter disregard for human life" in the territory.
In a statement, the agencies warned of severe aid shortages and hunger since Israel resumed its all-out assault.
The death toll has risen since the war restarted on 18 March and included the deadliest week for Gaza's children of the past year.
No new humanitarian supplies have entered the Palestinian enclave since Israel blocked the entry of aid trucks on 2 March.
Talks for the next stage of the truce and a deal for the release of the remaining hostages held by Hamas are stalled.
"More than 2.1 million people are trapped, bombed and starved again, while, at crossing points, food, medicine, fuel and shelter supplies are piling up, and vital equipment is stuck," the statement said.
It was co-signed by the heads of six UN agencies including its aid coordination organisation (OCHA) and the World Food Programme.
At least 1,000 children were killed or injured during the first week after fighting resumed, the statement added, describing that week's death toll as the highest for children of the past year.
"We are witnessing acts of war in Gaza that show an utter disregard for human life ... We appeal to world leaders to act - firmly, urgently and decisively - to ensure the basic principles of international humanitarian law are upheld," the statement read.
Israel denies violating humanitarian law in the territory and blames Hamas fighters for harm to civilians for operating among them, which the fighters deny.
The agencies also warned of critical food and medical shortages in Gaza.
Twenty-five bakeries supported by the World Food Programme during the ceasefire had to close due to flour and cooking gas shortages, it said.
The leaders of France, Egypt and Jordan have also called for an "immediate return" to the truce.
They also said that the Palestinian Authority alone must be in charge of the post-war governance of Gaza.
"Governance, law and order, and security in Gaza, as well as in all Palestinian territories, must be the sole responsibility of a strengthened Palestinian Authority," the leaders said in a joint statement.
More than 50,000 Palestinians have been killed by the Israeli campaign in Gaza, according to Hamas-run health ministry.
The war began after thousands of Hamas-led gunmen attacked communities in southern Israel on 7 October 2023, Israel said that 1,200 people died and 251 hostages were abducted.
One dead after Israeli strike on Lebanon
One person has died in an Israeli strike on southern Lebanon, the country health ministry said, in the latest raid despite a delicate truce between Israel and Hezbollah and after a US envoy visited.
The "Israeli enemy" drone attack on Taybeh near the border "led to the death of one citizen", the ministry said in a statement.
The official National News Agency (NNA) said the strike hit "in front of a motorcycle repair shop" in the town, in the Marjayoun area.
The Israeli military said it was "looking into" the reports.
Israel has continued to launch strikes on Lebanon since a 27 November ceasefire that largely halted more than a year of hostilities with Hezbollah, including two months of war.
The truce accord was based on a UN Security Council resolution that said Lebanese troops and peacekeepers should be the only forces in southern Lebanon and calls for the disarmament of all non-state groups.
Visiting US deputy special envoy for the Middle East Morgan Ortagus discussed the situation, including Hezbollah's disarmament., with senior Lebanese officials at the weekend.
Economic reforms were also on the agenda.
In an interview with Lebanese television channel LBCI, Mr Ortagus said the United States continues to press the country's government "to fully fulfil the cessation of hostilities, and that includes disarming Hezbollah and all militias", adding it should happen "as soon as possible".
Hezbollah was left severely weakened in the latest conflict with Israel.
