Israel launched its offensive in Gaza City on Tuesday, threatening to overwhelm a city already in ruins from nearly two years of raids and bombardment. Vehicles strapped with mattresses and other belongings clogged a coastal road as thousands of Palestinians fled, but hundreds of thousands more remain.

The operation into the largest Palestinian city further escalates a conflict that has roiled the Middle East and likely pushes any ceasefire farther out of reach. The military wouldn’t offer a timeline for the offensive, which it says aims to “destroy Hamas’ military infrastructure,” but Israeli media suggested it could take months.

It began the same day that independent experts commissioned by the United Nations’ Human Rights Council accused Israel of committing genocide in Gaza. Israel rejected the allegation, calling the report “distorted and false.”

Israeli Defense Minister Israel Katz declared that “Gaza is burning” as the operation began. Heavy bombardment battered the city overnight and into the morning.

Israeli forces have carried out multiple large-scale raids into Gaza City over the course of the war, causing mass displacement and heavy destruction, only to see militants regroup later. This time, Israel has vowed to take control of the entire city, which experts say is experiencing famine.

An Israeli military official, speaking on condition of anonymity in line with military guidelines, said that the “main phase” of the Gaza City operation had begun. Airstrikes have pounded Gaza City for weeks, knocking down several high-rises.

The official said the Israeli military believes there are approximately 2,000 to 3,000 Hamas militants left in Gaza City, as well as tunnels used by the militant group. Hamas’ military capabilities have been vastly diminished over nearly two years of war, and nowadays it mainly carries out guerrilla-style attacks, with small groups of fighters planting explosives or attacking military outposts before melting away.

An estimated 1 million Palestinians were living in the Gaza City region before warnings to evacuate began ahead of the offensive, and the Israeli military estimates 350,000 people have left the city.

A U.N. estimate on Monday, however, said that over 220,000 Palestinians have fled northern Gaza over the past month.

By the end of the current operation, an Israeli military graphic suggested its troops hope to control all of the Gaza Strip except for a large swath along the coast.

Palestinian residents reported heavy strikes across Gaza City on Tuesday morning, with hospitals in the city saying there were at least 69 deaths.

The war in Gaza began when Hamas-led militants stormed into southern Israel on Oct. 7, 2023, killing around 1,200 people, mostly civilians, and abducting 251. Forty-eight hostages, fewer than half believed to be alive, remain in Gaza.

Israel’s retaliatory offensive has killed more than 64,900 Palestinians, according to Gaza’s Health Ministry, which doesn’t say how many were civilians or combatants. The ministry, which is part of the Hamas-run government and staffed by medical professionals, says women and children make up around half the dead.

Overnight, families of the hostages still being held in Gaza gathered outside of Prime Minister Benjamin Netanyahu's residence, imploring him to stop the offensive.

Israel believes around 20 of the hostages are alive. Hamas has said it will only free remaining captives in return for Palestinian prisoners, a lasting ceasefire and an Israeli withdrawal from Gaza.