Hamas said on Friday it was "ready" for an invasion of Gaza as Israel said it was "extending" its ground operation after air strikes cut communications across the shattered Palestinian territory.
"Following the series of strikes of the last days, the ground forces are extending the ground operation tonight," military spokesman Daniel Hagari told reporters after two straight nights of tank incursions into the Gaza Strip.
A top Hamas official said it was "ready" for an Israeli ground invasion.
"If (Prime Minister Benjamin) Netanyahu decides to enter Gaza tonight, the resistance is ready," said Ezzat al-Rishaq, a senior member of the Hamas political bureau, on Telegram social media.
"The remains of his soldiers will be swallowed up by the land of Gaza."
Israel's military said it had increased its strikes "in a very significant way", as AFP live footage captured intense bombardment of northern Gaza.
Air strike after air strike lit up the night sky as thick black smoke clouded the horizon.
Hamas's armed wing, the Ezzedine al-Qassam Brigades, said on its Telegram channel it responded with "salvos of rockets".
Hamas said all internet connections and communications across Gaza had been cut, and accused Israel of taking the measure "to perpetrate massacres with bloody retaliatory strikes from the air, land and sea".
The Palestinian Red Crescent Society said ambulance services had been disrupted.
"We have completely lost contact with the operations room in the Gaza Strip and all our teams operating there," it said on X, formerly Twitter.
Hamas called on the world to "act immediately" to stop Israel attacking Gaza.
Israel has heavily bombarded Gaza since Hamas gunmen stormed across the border on October 7, killing 1,400 people, mostly civilians, and kidnapping over 220 others, according to Israeli officials.
The Hamas-run health ministry said Friday Israeli strikes on Gaza had now killed 7,326 people, mainly civilians and many of them children.
The White House said the United States backs a "humanitarian pause" so aid can get into Gaza.
"We would support humanitarian pauses for stuff getting in, as well as for people getting out, and that includes pushing for fuel to get in and for the restoration of electrical power," National Security Council spokesman John Kirby said.
UN Secretary-General Antonio Guterres warned that Gaza faces "an unprecedented avalanche of human suffering" because of the lack of food, water and power during Israeli bombing in response to the October 7 attack.
"I repeat my call for a humanitarian ceasefire, the unconditional release of all hostages, and the delivery of life-saving supplies," Guterres said in a statement.
"Misery is growing by the minute. Without a fundamental change, the people of Gaza will face an unprecedented avalanche of human suffering."
The UN agency for Palestinian refugees had earlier warned that "many more will die" in Gaza from catastrophic shortages after nearly three weeks of bombardment by Israel.
The UN human rights office also raised the alarm over "war crimes" being committed as the Israel-Hamas conflict raged for a 21st day.
Concern is growing about regional fallout from the conflict, with the United States warning Iran against escalation while striking facilities in Syria it says were used by Iran's Islamic Revolutionary Guard Corps and others.
Israel's military accused Hamas of using hospitals in Gaza as operations centres for directing attacks, an allegation Hamas swiftly denied.
"Hamas wages war from hospitals," in the territory, Hagari said, and alleged the group was also using fuel stored in these facilities for its operations.
A senior Hamas official said the allegation had "no basis in truth".
- War crimes on both sides -
Israel has cut supplies of food, water and power to Gaza, notably blocking all deliveries of fuel saying it would be exploited by Hamas to manufacture weapons and explosives.
"People in Gaza are dying, they are not only dying from bombs and strikes, soon many more will die from the consequences of (the) siege," said Philippe Lazzarini, chief of the UN agency for Palestinian refugee (UNRWA).
"Basic services are crumbling, medicine is running out, food and water are running out, the streets of Gaza have started overflowing with sewage," he said of the densely populated territory where 45 percent of housing is reported to have been damaged or destroyed.
In Geneva, the UN human rights office raised the alarm over war crimes, saying "the atrocious attacks by Hamas... amounted to war crimes" but also pointing to Israel's Gaza bombardment.
- 'Nothing more than crumbs' -
A first tranche of critically needed aid was allowed in at the weekend, but since then only 74 trucks have crossed. Before the conflict, the UN says an average of 500 trucks entered Gaza every day.
"These few trucks are nothing more than crumbs that will not make a difference," Lazzarini said, insisting Gaza needed a "meaningful and uninterrupted aid flow" and a "humanitarian ceasefire to ensure this aid reaches those in need".
His words echoed a call from EU leaders on Thursday for "continued, rapid, safe and unhindered humanitarian access and aid".
A first team of six medics from the International Committee of the Red Cross entered Gaza Friday via its Rafah crossing with Egypt, along with six aid trucks, the ICRC said.
Between the bombardments and the fuel shortages, 12 of Gaza's 35 hospitals have been forced to close, and UNRWA said it has had to "significantly reduce its operations".
With tens of thousands of Israeli troops massed along the Gaza border ahead of a widely expected ground offensive, the army said it had staged another brief ground incursion into Gaza on Thursday night, the second in as many days.
Hamas said Israel had also tried to stage "a large-scale amphibious operation" on the coast around the southern town of Rafah but it had been thwarted.
Israel confirmed the dawn operation, saying troops had struck "Hamas military infrastructure and... a compound" used by militants.
- 'Like the living dead' -
The army also updated to 229 the number of hostages held by Hamas, many of whom hold foreign passports, with their families frantic about their fate.
"I have never felt such a feeling of helplessness," said 23-year-old Ella Ben Ami whose parents were kidnapped. With recurring nightmares every single night, she says she feels "like the living dead".
Militants also fired rockets on Friday towards Tel Aviv. One struck the city, wounding three people, medics said.
Violence has also risen sharply in the occupied West Bank since the October 7 attacks, with more than 100 Palestinians killed and over 1,900 wounded.
Another four Palestinians were killed Friday during Israeli raids in the northern cities of Jenin and Qalqilya, the health ministry said.