Smoke from an explosion rises in Gaza as seen from southern Israel, on Sunday. Reuters

Israel and Hamas brushed off international calls to renew an expired truce on Saturday as airstrikes pounded Hamas targets in Gaza and Palestinian groups launched volleys of rockets.

Seven Palestinians were killed and several others were injured in an Israeli raid on a house east of Rafah city in southern Gaza, the Hamas-led interior ministry said on Sunday.

Smoke again clouded the sky over the north of the Palestinian territory, whose Hamas government said 247 people had been killed since a pause in hostilities expired early Friday and combat resumed.

The Israeli army said it had conducted more than 400 strikes in Gaza since a ceasefire collapsed on Friday.

In Israel, the military's Home Front Command reported 40 missile alerts in the south and centre of the country, and the Palestinian groups Hamas and Islamic Jihad announced "rocket barrages" against multiple Israeli cities and towns including Tel Aviv.

Israeli soldiers take position against Palestinian group Hamas, in a location given as Jabalya, in Gaza on Sunday. Reuters

"Over 250 rockets have been fired at Israel since Friday morning," Israeli military spokesman Lieutenant Colonel Peter Lerner told reporters.

According to the United Nations, an estimated 1.7 million people in Gaza — more than two-thirds of the population — have been displaced by eight weeks of war.

Fadel Naim, chief doctor at the Al-Ahli Arab hospital in Gaza City, said his morgue had received 30 bodies on Saturday, including seven children.

"The planes bombed our houses: three bombs, three houses destroyed," Nemr al-Bel, 43, told the media, adding he had counted 10 dead in his family and "13 more still under the rubble".

Gazans are short of food, water and other essentials, and many homes have been destroyed. UN agencies have declared a humanitarian catastrophe, although some aid trucks did arrive Saturday.

Israeli soldiers take position during the ongoing ground operation in Gaza. Reuters

"Homes, hospitals and other infrastructure critical to the survival of the civilian population have suffered colossal destruction," said Pascal Hundt, head of operations in Gaza for the International Committee of the Red Cross (ICRC).

"Current conditions do not allow for a meaningful humanitarian response, and I fear will spell disaster for the civilian population," he added.

After the truce between Israel and Hamas expired on Friday, Israel had told NGOs not to bring aid convoys across the Rafah border crossing from Egypt, the Palestine Red Crescent Society had said.

But on Saturday, the charity said its Egyptian colleagues had managed to send over a number of trucks.

Agencies