Israeli military strikes across the Gaza Strip killed at least 21 Palestinians, local health authorities said on Monday, as Israeli forces operated in Rafah near the border with Egypt, escalating a new week-long aerial and ground offensive.

Health officials said Israel has killed nearly 700 Palestinians since it resumed attacks on Gaza last Tuesday, ending weeks of relative calm after a ceasefire in January. It said the deaths included at least 400 women and children.

Islamist group Hamas said several of its senior political and security officials had also been killed. Israel says it resumed its military operations to force Hamas to release the remaining hostages it is holding in Gaza.

It says it does its best to reduce harm to civilians and has questioned the death toll by health authorities in the Hamas-run enclave.

Israel's Defence Minister said his country was fighting against Hamas and not Gaza civilians.

"But when Hamas fights in civilian dress, from civilian homes, and from behind civilians, it puts civilians in danger and they pay a horrible price. That is why we are urging Gazans to evacuate combat zones," Katz said on X.

Hamas denies using the civilian population and property for military purposes.

In Rafah, the municipality said thousands of people were trapped inside the Tel Al-Sultan area, where the Israeli military had sent some of its forces.

"Contacts with the neighborhood are cut off completely and the fate of (people) is unknown. Families are trapped among the ruins, with no water, no food, no medicine, amid a total collapse of healthcare services," it said in a statement.

The Palestinian Civil Emergency Service said 50,000 residents remained trapped in Rafah.

The Israeli military said troops had encircled Tel Al-Sultan to dismantle "terror infrastructure sites and eliminate terrorists in the area."

Palestinian officials on Sunday put the death toll from nearly 18 months of conflict at over 50,000.

Israel launched its offensive in Gaza after Hamas fighters stormed southern Israel on October 7, 2023, killing 1,200 people, mostly civilians, and taking more than 250 hostages, according to Israeli tallies.