JERUSALEM >> Prime Minister Benjamin Netanyahu said in a televised news conference Saturday that Israel’s forces had entered the Gaza Strip, calling it his country’s “second war of independence” and warning Israelis to expect a “long and difficult” campaign to eradicate Hamas.

Netanyahu said the troops had gone into Gaza on Friday evening, beginning “the second stage of the war.” The Israeli military has not publicly described the operation as an invasion and released only brief footage of its advance.

The ground assault in the northern part of the Gaza Strip was shrouded in secrecy and ambiguity and accompanied by an enormous aerial and artillery bombardment. It was the most sustained fighting against Hamas since the war began three weeks ago.

Hamas’ armed wing confirmed Friday night and Saturday afternoon that the battle with Israeli ground forces had been joined. Shortly before Netanyahu’s remarks, a spokesperson for the group, Abu Obeida, greeted the relentless airstrikes and the apparent beginnings of the ground incursion with defiance. Hamas would make Israel “taste new ways of death,” the spokesperson said.

With Gaza’s internet connections and phone lines down, few Palestinian accounts have emerged, making it difficult to assess the extent of the military action.

Palestinian telecommunication networks blamed Israel’s bombardment for the wide-scale communications blackout, which left most people in Gaza unreachable by phone. The blackout sparked fear and panic, according to residents who were able to reach the outside world, as people struggled to get information or check on family and friends.

“The explosions were happening to our left, to our right — from all directions,” Helmi Mousa, a Gaza City resident who huddled with his wife in their ninth-floor apartment, said Saturday.

The bombardments were so intense overnight, he said, that even amid a sustained electricity blackout, their apartment was filled with the light of explosions.

“Our building was shaking, swaying back and forth,” said Mousa, who was reached on his foreign-registered cellphone, one of the few connections still working. “We could hear the booms, the airplanes, the strikes.”

The Israeli military said Saturday that warplanes had focused 150 strikes on the vast networks of tunnels in Gaza, which present a formidable challenge to Israel’s stated goal of dismantling the military and governing capabilities of Hamas, the group that controls Gaza.

The chief Israeli military spokesperson, Rear Adm. Daniel Hagari, told reporters Saturday night that the Israeli military was “gradually increasing its ground activity in the Gaza Strip and the scale of its forces.”

“It will take time and we will adapt ourselves to developing events and carry out the war aims,” he said.

From all reports, the next stage promises to be long and bloody. Hamas has constructed a sprawling network of subterranean pathways and chambers, some as deep as 130 feet below ground and packed with weapons and ammunition, and where the group is holding more than 200 hostages, Israel said.

Saudi Arabia and other Arab governments have warned that a full-scale war in Gaza could be catastrophic for the Middle East. Tensions also have spiked between Israel and Turkey in recent days, particularly over remarks by Turkish President Recep Tayyip Erdogan defending Hamas and criticizing Israel for its campaign in Gaza.

For Gaza residents living above the tunnels, one of the most frightening propositions will be how to survive a war where the ground below them is part of the battlefield.

Until this weekend, the outside world was receiving updates from Gaza-based journalists and representatives of aid agencies on the worsening humanitarian conditions in Gaza, where food, drinking water, medical supplies and fuel are scarce. But the steady deterioration of internet service in the territory and the sudden collapse of cellular networks Friday have contributed to a much more opaque picture of the situation on the ground.

A number of United Nations agencies have reported losing contact with their local staff in Gaza. Jan Egeland, head of the Norwegian Refugee Council aid group, said it could no longer reach its 54 staff members in Gaza.

“They flee for their lives with their families in both the north & south of a densely populated place with no escape from the bombardment,” he wrote on X, formerly Twitter.

One of Gaza’s cellphone providers, Paltel Group, said in a statement that “continuous bombardment” had severed all remaining fiber-optic connections with the outside world.

The lack of cellular services also cut off residents inside Gaza Strip from one another. Tedros Adhanom Ghebreyesus, head of the World Health Organization, said on X that the blackout was “making it impossible for ambulances to reach the injured” and that it was not possible to get patients to safety in the circumstances.

The trickle of information that emerged from Gaza on Saturday came from those with satellite phones and other devices not reliant on the local networks.

On the Al Jazeera news network, which continued to broadcast from Gaza on Saturday, a spokesperson for the Hamas-controlled Gaza Health Ministry read a statement saying that 377 Palestinians had been killed by Israeli strikes in “recent hours,” raising the ministry’s death toll in the territory to 7,703, of which 3,195 were reported to be children.

Although the ministry has released information identifying the victims, the figures could not be independently verified.

The United Nations estimates that about 1 million of the more than 2 million residents of Gaza have been displaced from their homes.

Israeli has acknowledged the civilian toll of its airstrikes, but says it cannot reach its ultimate goal of ousting Hamas and its leadership without dismantling a network that operates above and below ground, often woven into residential areas.

One of those civilian areas, Israel said Friday, is al-Shifa hospital, where more than 60,000 people are sheltering in the expectation it will provide refuge from the bombing. But Israel contends it hides an important Hamas command center, making it a prime military target.

“This is where they direct rocket attacks, command Hamas forces,” Hagari said at a news conference in Tel Aviv, Israel, on Friday.

Over the past week, under the accumulated trauma of Israeli airstrikes, Gaza residents say the bombs come mostly without warning and hit indiscriminately, leading to widespread hopelessness and the feeling that imminent death is inevitable.

“You can’t imagine the feeling,” said Nayrouz Qarmout, a Palestinian author who lives in the Gaza Strip. “You are not safe. All places are targets, so you think of dying at any time.”

In Gaza City, Helmi said most of his neighbors have fled. Of the nearly 20 families who lived in his building before the war, four remain. “We’d rather die in our homes,” he said.