More than 700 people have been killed in the last 24 hours, according to Gaza's health ministry, despite US assurances that it had urged Israel to show "restraint" as it resumed its war on the Palestinian enclave.

Israel's military on Sunday ordered more areas in and around Gaza's second-largest city of Khan Younis to evacuate, as it shifted its offensive to the southern half of the territory, reports Al Jazeera.

Heavy bombardments were reported overnight and into Sunday in the area of Khan Younis and the southern city of Rafah, as well as parts of the north that had been the focus of Israel's blistering air and ground campaign.

Many of the territory’s 2.3 million people are crammed in the south after Israeli forces ordered civilians to leave the north in the early days of the 2-month-old war.

With the resumption of fighting, hopes receded that another temporary truce could be negotiated as Israel ordered its negotiators home from Qatar.

UN monitors said in a report issued before the latest evacuation orders that the areas residents were told to leave make up about one-quarter of the territory of Gaza. The report said that these areas were home to nearly 800,000 people before the war.

Ahead of a resumption of fighting, the US, Israel’s closest ally, had warned Israel to avoid significant new mass displacement, but these appeals seem to have fallen on deaf ears.

Bombardments on Saturday destroyed a block of about 50 residential buildings in the Shijaiyah neighborhood of Gaza City and a six-story building in the urban refugee camp of Jabaliya on the northern edge of the city, said the UN Office for the Coordination of Humanitarian Affairs.