By MELANIE LIDMAN, JON GAMBRELL and SAMY MAGDY, Associated Press

JERUSALEM (AP) -- 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.

One woman, Saud al-Sakani, said her daughter, son-in-law and their children were killed in a strike that flattened their home with about 40 people inside. "An entire family!" she cried, weeping over their bodies at Shifa Hospital's morgue. "Many are still under the rubble."

On a brief visit to the region, U.S. Secretary of State Marco Rubio warned that there was a "very short window of time in which a deal can happen" to end the war.

Israel also bombed Yemen's port city of Hodeida in response to drone and missile fire from Iran-backed Houthi rebels, who say they are acting in solidarity with the Palestinians.

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.

Ismail Zaydah, 39, said he fled from his home in Gaza City's Sheikh Radwan neighborhood to an area near the coastal road. He said trucks carrying people south to an Israeli-designated humanitarian zone charge around $1,000, even as many families in Gaza City are starving.

"We fled with nothing but a few pieces of clothing. People are pitching their tents in western Gaza City, and they are sleeping among human waste because there is no place for them to go," he said.

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.

"A very tough night in Gaza," Dr. Mohamed Abu Selmiya, the director of Shifa Hospital, told The Associated Press. "The bombing did not stop for a single moment."

Several women gathered at the hospital's morgue, where AP footage showed many dead in body bags.

Shifa received the bodies of 49 people, including 22 children, according to Dr. Rami Mhanna, a hospital official, who said dozens of wounded had also come into the facility. Al-Ahli Hospital received 17 bodies, and Al-Quds three.

The Israeli military did not immediately respond to requests for comment on the deadly strikes but in the past has accused Hamas of building military infrastructure inside civilian areas.

The war in Gaza began when Hamas 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.

"Netanyahu gave the order to bomb my child," said Anat Angrast, whose son is held in Gaza. "He knows that Matan is in immediate danger due to the Gaza operation, yet he decided to bomb him to death. He is the only one who will decide whether Matan lives or dies."

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.

On a visit to Israel, Rubio suggested that there might still be time for a negotiated end the war.

"At some point, this has to end. At some point, Hamas has to be defanged, and we hope it can happen through a negotiation," he said. "But I think time, unfortunately, is running out."

He continued on to Qatar, where he met with its ruling emir. Qatar is incensed over an Israeli strike last week that killed five Hamas members and a local security official.

Rubio thanked Qatar, which has been a key negotiator in efforts to reach a ceasefire, for playing that role, according to a statement from his office, which did not directly acknowledge the Israeli strike. He also highlighted the countries' close ties.

Arab and Muslim nations denounced the strike at a summit Monday but stopped short of any major action targeting Israel.

Egypt, which has had a peace deal with Israel for decades and has also served as a mediator in the war, appears to be losing its patience.

Egypt's president, Abdel-Fattah el-Sissi, described Israel as "an enemy" in a fiery speech at the Qatar summit Monday. It was the first time an Egyptian leader used the term since the two countries established diplomatic ties in 1979, said Diaa Rashwan, head of Egypt's State Information Service.

Egypt was the first Arab country to establish ties with Israel and their peace treaty is seen as a cornerstone for stability in the volatile region.

El-Sissi's "enemy" comment played prominently across Egyptian newspapers' front pages on Tuesday and while Cairo has taken no steps to change its status with Israel, the Egyptian government likely is trying to signal just how seriously it takes Israel's recent actions.

Israel's military begins its ground offensive in Gaza City and thousands of residents flee