Fierce air and artillery strikes rang out in Gaza City early on Monday as Israeli troops backed by tanks pressed into the Palestinian enclave with a ground assault that prompted more international calls for civilians to be protected.

Israel's military said it had struck more than 600 militant targets over the past few days as it expanded ground operations in the Gaza Strip, where Palestinian civilians are in dire need of fuel, food and clean water as the war enters its fourth week.

"IDF troops killed dozens of terrorists who barricaded themselves in buildings and tunnels, and attempted to attack the troops," a military statement said.

Israel began a major push into the Gaza Strip on Friday and reiterated calls for civilians to move from the north of the tiny coastal enclave to the south as it tries to root out Hamas fighters it says are hiding in a labyrinth of tunnels under Gaza City.

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In what appeared to be an effort to cut off the city, Israeli forces carried out dozens of air strikes on its eastern side, residents said, with some reporting the roar of tanks rolling in amid heavy exchanges of fire.

Internet and phone connections cut off

To the west, where Israel has placed tanks on the Mediterranean coast, the north-south coast road was hit several times, residents said. Internet and phone connections remained largely cut off in the north, making communication difficult.

Many Palestinians have remained in Gaza City, afraid to lose their homes and concerned by news of Israeli air strikes further south. Medical officials in Al-Shifa and Al-Quds hospitals said air strikes had hit near their buildings. 

The UN humanitarian office OCHR said 117,000 civilians are sheltering alongside thousands of patients and doctors in hospitals in the north. 

Air strikes could also be heard in the southern towns of Rafah near Gaza's border crossing with Egypt, the only one not blocked by Israel, as well as east of Khan Younis, where Palestinian media said Hamas clashed with Israeli troops.

Phone and internet cuts which blacked out Gaza on Friday had eased and OCHR said on Monday services were "largely restored" although telecoms providers have said some areas on the north were still down.

Clashes in the West Bank

Israel has said 1,400 people were killed when Hamas-led militants stormed through the south of the country on October 7 and took 229 hostage. Hamas has released four so far and said 50 have been killed in retaliatory strikes.

Medical authorities in Hamas-run Gaza, which has a population of 2.3 million people, said on Sunday 8,005 people - including 3,324 minors - had been killed.

OCHR said rescuers were struggling to reach people.

"As of October 29, about 1,800 people, including at least 940 children, have been reported missing and may be trapped or dead under the rubble, awaiting rescue or recovery," it said.

It also said that armed groups continued firing rockets at Israel indiscriminately, with no fatalities reported.

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