The Israeli military has knocked out communications and created a near-blackout of information in Gaza as it announced an expansion of ground operations and warned residents of Gaza City to move south.
Israel Defence Forces (IDF) entered northern Gaza overnight and the military said its forces remained in Gaza on Saturday morning.
More than 7,300 Palestinians have now been killed in airstrikes, Gaza authorities say, and Israel today again urged people to evacuate northern Gaza.
"We moved to the next stage in the war," Israeli defence minister Yoav Gallant said in remarks broadcast Saturday. He said that the "campaign" would continue "until further notice".
Israel-Gaza latest: Heaviest night of strikes on Gaza since the conflict began
Overnight, Israeli fighter jets hit 150 underground targets in the northern Gaza Strip, the IDF said on Saturday.
This included "terror tunnels, underground combat spaces and additional underground infrastructure" and resulted in the deaths of several Hamas members, it added.
The Palestinian telecom provider, Paltel, said the bombardment caused "complete disruption" of internet, cellular and landline services as the besieged enclave's 2.3 million people were largely cut off from contact with the outside world.
Hamas has said its fighters were clashing with Israeli troops in Gaza's northeastern town of Beit Hanoun and in the central area of al Bureij.
"The al Qassam brigades and all the Palestinian resistance forces are completely ready to confront (Israel's) aggression with full force and frustrate its incursions," Hamas said in a statement early on Saturday.
"Netanyahu and his defeated army will not be able to achieve any military victory."
The Israeli military also said it has killed the head of Hamas's aerial wing, who had helped plan the 7 October attack and was responsible for the paragliders who flew across the border.
The IDF's announcement comes after it said it had carried out more raids into Gaza - including a naval operation.
Key developments include:
- Israel says ground forces "expanding their activity"
- IDF says it hit 150 underground targets overnight
- More than 7,300 Palestinians now killed in airstrikes, Gaza authorities say
- Head of Hamas aerial unit - responsible for paraglider attack - killed, Israel says
- Hamas says its fighters clashed with Israeli troops in northeast Gaza
The IDF said troops had used vessels to attack "Hamas military infrastructure", with support from aircraft, along the coast in the southern Gaza Strip on Thursday night.
Officials released footage of what they said was the raid, but did not go into further details.
The video showed explosions near the sea and soldiers firing their weapons in the dark.
However, Hamas disputed the IDF's version of events in a statement and said its forces had repelled the raiders, Israeli media reported.
Israeli forces also said they carried out a separate ground raid on the outskirts of Gaza City on Thursday night, as part of a second wave of recent incursions into the territory.
Israel has amassed hundreds of thousands of troops along the border with Gaza ahead of an expected ground offensive.
However, according to Sky News's military analyst, Sean Bell, any offensive is likely to start with moving tanks and armoured vehicles across the border.
"There are lots of phases military operations go to, to gradually ramp up and de-risk the ultimate invasion," he said.
"And we've seen that over the last few nights - an increase in the bombing campaign, what the IDF calls raids - all of this is testing Hamas's defences and what threats will face the IDF as they get closer to mounting the offensive.
"The first phase of that is likely to be an armoured push over the border, probably to encircle the city of Gaza.
"But the challenge is the IDF doing an urban battle on foot - clearing Gaza City and worse the tunnels. I think that will be an extremely dangerous undertaking."
Meanwhile, Ayman Safadi, the foreign minister of Israel's neighbour Jordan, on Friday accused Israel of "launching a ground war on Gaza".
"[The] outcome will be a humanitarian catastrophe of epic proportions for years to come," he said in a post on X, formerly known as Twitter.
He called on the UN General Assembly to support a resolution, put forward by Jordan on behalf of Arab nations, calling for a humanitarian ceasefire between Israel and Hamas.
The resolution by the 193-strong world body was approved on Friday - despite Israel and the US both voting against it and the UK abstaining.
However, it does not force any action on either Israel or Hamas.
Israel accuses Hamas of launching attacks from Gaza hospitals
At an earlier briefing, Rear Admiral Hagari accused Hamas of launching attacks from hospitals in Gaza.
He claimed the Israeli authorities had "concrete evidence" that hundreds of Hamas fighters who took part in the 7 October terrorist atrocity in southern Israel afterwards "flooded" into Shifa hospital, the largest medical complex in the Gaza Strip.
"Right now, terrorists move freely in Shifa hospital and other hospitals in Gaza," the spokesperson said.
"Hamas's use of hospitals is systematic... When medical facilities are used for terror purposes, they are liable to lose their protection from attack in accordance with international law.
"The IDF (Israel Defence Forces) will continue making efforts to minimise harm to the civilian population and will continue to act in accordance with international law."
It was not immediately possible to independently verify the claims.
Another IDF spokesperson, Lieutenant Colonel Peter Lerner, was asked by Sky News if the briefing was to soften the ground for the Israeli military to begin strikes on hospitals.
Asked if hospitals would no longer be afforded protection under international law, he said: "If these actions continue from hospitals, under certain conditions, hospitals could indeed lose the protections that they are entitled to.
"They (Hamas) have to leave hospitals, they have to let people leave hospitals, they can't tell them to say and hold them hostage in hospitals."
However, a doctor from north London, who is currently working in Gaza, claimed the Israeli briefing was an "outlandish excuse" to target hospitals.
Dr Ghassan Abu-Sittah said: "At the end of the day, what they need to be reminded of, continuously, by everybody, and press included, is that the targeting of any hospital is a war crime, regardless of what outlandish excuses they might provide."
However, Mark Regev, a senior adviser to Israel's prime minister, Benjamin Netanyahu, said those in Gaza who speak out against Hamas can "face consequences".
Speaking to Sky News, he said: "If that doctor knows, as we do, that Hamas has built a headquarters in the basement of his hospital, can he say so to Sky?
"Of course, he cannot."
More than one million have fled their homes
According to Gaza authorities, more than 7,300 Palestinians have now been killed in waves of airstrikes by Israel in retaliation for a cross-border massacre carried out by Hamas in the south of the country on 7 October.
Officials said the dead include more than 3,000 children and over 1,500 women.
More than 1,400 people in Israel, mostly civilians, were killed during the initial Hamas attack, according to the Israeli government.
It also said Hamas is holding at least 229 captives inside Gaza, including women, children and the elderly.
The overall number of deaths far outstrips the combined total of all four previous conflicts between Israel and Hamas, estimated at around 4,000.
More than one million people in Gaza have fled their homes, with many following Israeli orders to evacuate to the south.
'Humanitarian catastrophe is deepening'
It comes as six International Committee of the Red Cross (ICRC) trucks arrived in Gaza carrying medical and water purification supplies.
The ICRC's Fabrizio Carboni said: "This crucial humanitarian assistance is a small dose of relief, but it's not enough.
"This humanitarian catastrophe is deepening by the hour."
The head of the UN agency for Palestinian refugees has warned remaining public services in Gaza are collapsing fast with fuel and food shortages.
UNRWA chief Philippe Lazzarini said the international community "seems to have turned its back on Gaza."
He also said Israel must allow more aid into Gaza amid a blockade he said is being used to "collectively punish more than two million people".
Gaza's sole power station shut down due to lack of fuel days after the start of the war, and Israel has barred all fuel deliveries, saying it believes Hamas would steal them for military purposes.
Internet and mobile phone services have also been cut off in the Gaza Strip, a local telecoms firm and the Red Crescent said.