Netanyahu, speaking after his security cabinet on Friday approved a much-criticised plan to take control of Gaza City said he had no choice but to "complete the job" and defeat Hamas to free hostages seized from Israel.
Gaza City, the enclave's most populous centre, came under escalating Israeli air strikes late on Sunday, witnesses said. At least five people were killed at a sandwich shop in the Sabra neighbourhood, health officials at Shifa Hospital said.
Palestinian media said a missile hit a tent used by journalists near the hospital, and the head of Shifa Hospital, Muhammad Abu Salamiyah, said on Al Jazeera television that seven people were killed there. Tank fire was also reported in the area.
Al Jazeera said five of its staff died in the attack including journalists Anas Al Sharif and Mohammed Qreiqeh and three photojournalists.
Israel's military said it targeted and killed Sharif, whom it claimed was the head of a Hamas cell posing as a journalist. It said the accusation had been confirmed by intelligence and documents found in Gaza. UN Special Rapporteur Irene Khan said last month the claims were unsubstantiated.
Netanyahu's office said the prime minister had spoken with US President Donald Trump about "Israel's plans to take control of the remaining Hamas strongholds in Gaza."
He said the new Gaza offensive aimed to tackle two remaining Hamas strongholds in what he said was his only option because of the Palestinian group's refusal to lay down its arms. Hamas says it will not disarm unless an independent Palestinian state is established.
It was not clear when the offensive, which would be the latest in successive attempts by the Israeli military to clear the militants from Gaza City, would begin.
"The timeline that we set for the action is fairly quickly. We want, first of all, to enable safe zones to be established so the civilian population of Gaza City can move out," he said.
The city, home to a million people before the two-year-old war, would be moved into "safe zones", he said. Palestinians say these have not protected them from Israeli fire in the past.
Israel's military chief has voiced opposition to occupying the entire Gaza Strip and has warned that expanding the offensive could endanger the lives of hostages Hamas is still holding and draw its troops into protracted and deadly guerrilla warfare.
Netanyahu said his goal was not to occupy Gaza. "We want a security belt right next to our border, but we don't want to stay in Gaza. That's not our purpose," he said.
European representatives at the United Nations said famine was unfolding in Gaza and Israel's plan would only make things worse.
"Expanding military operations will only endanger the lives of all civilians in Gaza, including the remaining hostages, and result in further unnecessary suffering," Denmark, France, Greece, Slovenia and the United Kingdom said in a joint statement.
"This is a man-made crisis, and therefore urgent action is needed to halt starvation and to surge aid into Gaza," they said.
Malnutrition is widespread in the enclave due to what international aid agencies say is a deliberate plan by Israel to restrict aid. Israel rejects that allegation, blaming Hamas for the hunger among Palestinians and saying a lot of aid has been distributed.
The war began on October 7, 2023, when Hamas-led militants stormed into southern Israel and killed 1200 people and took 251 hostages. Israeli authorities say 20 of the remaining 50 hostages in Gaza are alive.
Israel's offensive since then has killed more than 61,000 Palestinians, according to health officials, and left much of the territory in ruins.
