Israel has said it plans to seize the city, where about a million Palestinians have been sheltering, as part of its declared aim of eliminating the militant group Hamas, and has intensified attacks on what it has called Hamas' last bastion.

The group's political leadership, which has engaged in on-and-off negotiations on a possible ceasefire and hostage release deal, was targeted by Israel in an airstrike in Doga on Tuesday in an attack that drew widespread condemnation. 

Qatar will host an emergency Arab-Islamic summit on Monday to discuss the next moves. Rubio said Washington wanted to talk about how to free the 48 hostages - of whom 20 are believed to be still alive - still held by Hamas in Gaza and rebuild the coastal strip.

"What's happened, has happened," he said. "We're gonna meet with them (the Israeli leadership). We're gonna talk about what the future holds," Rubio said before heading to Israel where he will stay until Tuesday.

He was expected to visit the Western Wall Jewish prayer site in Jerusalem on Sunday with Prime Minister Benjamin Netanyahu and hold talks with him during the visit.

US officials described Tuesday's strike on the territory of a close US ally as a unilateral escalation that did not serve American or Israeli interests. Rubio and US President Donald Trump both met Qatar's Prime Minister Mohammed bin Abdulrahman Al-Thani on Friday.

Netanyahu signed an agreement on Thursday to push ahead with a settlement expansion plan that would cut across West Bank land that the Palestinians seek for a state - a move the United Arab Emirates warned would undermine the US-brokered Abraham accords that normalised UAE relations with Israel.

Aid agencies say an Israeli takeover of Gaza City would be catastrophic for a population already facing widespread malnutrition.

Two more Palestinians have died of malnutrition and starvation in Gaza in the past 24 hours, the territory's health ministry said on Sunday, raising deaths from such causes to at least 422 people, including 145 children.

Israel, which blocked all food from entering Gaza for 11 weeks earlier this year, has been allowing more aid into the enclave since late July to prevent further food shortages, though the United Nations says far more is needed. 

It says it wants civilians to leave Gaza City before it sends more ground forces in. Tens of thousands of people are estimated to have left but hundreds of thousands remain in the area. Hamas has called on people not to leave. 

Israeli army forces have been operating inside at least four eastern suburbs for weeks, turning most of at least three of them into wastelands. It is closing in on the centre and the western areas of the territory, where most of the displaced people are taking shelter.

Prior to the latest assault, the United Nations had estimated that around a million people lived in and around the city, where it officially declared famine last month.

AFP footage showed exhausted families moving along the coastal road near Nuseirat south of Gaza City, with their belongings stacked high in vehicles.

In the city itself, "the bombardment hasn't stopped since dawn," said Umm Alaa Shaaban, 45, a resident of Tal al-Hawa district in Gaza City's southwest.

"We haven't slept all night... The sounds of shelling and explosions have not stopped until now," she told AFP.