Israel pounded the Hamas-run Gaza Strip with air and artillery strikes on Saturday after an intense night of attacks when it said 150 "underground targets" were hit.
No official toll was immediately given, but a Gaza civil defence official told AFP a "large number" of dead was feared from one of the most intense nights of attacks in Israel's war in response to the Hamas attacks on October 7.
Israel has been building up to a ground invasion since Hamas fighters crossed the border and killed 1,400 people, mainly civilians, and took more than 220 hostages, according to Israel.
The Hamas-controlled health ministry says that more than 7,300 people have been killed in Gaza, including about 3,000 children.
A thick haze of smoke covered Gaza and southern Israel after the night of heavy bombardment, according to AFP correspondents.
More air raids and artillery shelling were reported after daybreak but less intense than during the night.
The Gaza civil defence official told AFP: "There are a large number of martyrs and a large number of survivors under the rubble, and we cannot reach them," the official said.
Residents told AFP the Indonesian Hospital in Beit Lahia was damaged by a tank shell and there was major damage around Al-Shifa hospital, Gaza's biggest hospital where thousands of people have taken refuge.
The Israeli army has charged that Hamas fighters were using hospitals in Gaza to "wage war" against Israel.
Paramedics said many people were feared dead after an apartment block and nearby houses were destroyed at dawn at the Beach camp.
- 'Big plan' -
Since the October 7 attacks, Israel warned about 1.1 million people in
northern Gaza that they should move to the south.
The Israeli military believes the Hamas leadership and its main infrastructure is concentrated in the north.
An unnamed officer quoted by an Israeli military account on X, the former Twitter, said: "We are bombarding Gaza with an intensity that has never been seen before in the Gaza Strip. From the air, from the ground or from the underground -- the IDF (Israeli army) will eliminate every senior or junior terrorist and all Hamas terrorist infrastructure."
Just before the latest strikes, a senior Israeli officer said the raids did not mark the start of the ground invasion.
Another report adds from Ankara:Turkey's President Recep Tayyip Erdogan on Saturday called on Israel to "immediately stop this madness" and end its "attacks" on targets in Gaza after Israeli forces intensified strikes on the Palestinian territory.
"The Israeli bombardments on Gaza intensified last night and once again targeted women, children and innocent civilians and worsened the ongoing humanitarian crisis," Erdogan said on X. "Israel must immediately stop this madness and end its attacks."