After a night of heavy airstrikes, the Israeli military announced Tuesday that its expanded operation in Gaza City "to destroy Hamas' military infrastructure" has begun, and warned residents to move south. Israeli military spokesman Avichay Adree announced the expansion of Israel's operation in a post on X, renewing a warning for Gaza City's famine-stricken residents to evacuate.

Many Palestinians -- tens of thousands of whom had sought shelter in Gaza City after fleeing areas further north amid Israel's offensive against Hamas -- have said they're unable to evacuate due to overcrowding in southern Gaza and the high price of transport.

The Israel Defense Forces announced the launch of the next stage of "Operation Gideon Chariots," saying two divisions had begun pushing into the heart of Gaza City, with two regular divisions operating in the surrounding area. It said a third division would join the operation in the coming days.

"They will surround Gaza City on all sides," the IDF said.

After weeks of threatening an expansion of the Israeli military operation in Gaza City, Israeli Defense Minister Israel Katz also signaled on Tuesday that it had begun.

"Gaza is burning," he said early in the morning. "The (Israel military) is striking with an iron fist at the terrorist infrastructure and soldiers are fighting heroically to create the conditions for the release of the hostages and the defeat of Hamas. We will not relent and we will not go back -- until the completion of the mission."

The United Nations estimated on Monday that over 220,000 Palestinians have fled northern Gaza over the past month, after the Israeli military warned that all residents should leave Gaza City ahead of the operation. An estimated 1 million Palestinians were living in the region around Gaza City before the evacuation warnings.

Palestinian residents reported heavy strikes across Gaza City on Tuesday morning. The city's Shifa Hospital said it received the bodies of 20 people killed in a strike that hit multiple houses in a western neighborhood, with another 90 wounded arriving at the facility in recent hours.

"A very tough night in Gaza," Dr. Mohamed Abu Selmiyah, director of Shifa Hospital, told The Associated Press

"The bombing did not stop for a single moment," he said. "There are still bodies under the rubble."

The Israeli military did not respond to immediate requests for comment on the strikes but in the past has accused Hamas of building military infrastructure inside civilian areas, especially in Gaza City.

Meanwhile, U.S. Secretary of State Marco Rubio traveled Tuesday from Israel to the energy-rich nation of Qatar for talks with its ruling emir, whose country is still incensed over Israel's strike last week that killed five Hamas members and a local security official.

Arab and Muslim nations denounced the strike at a summit Monday but stopped short of any major action targeting Israel, highlighting the challenge of diplomatically pressuring any change in Israel's conduct.

Egypt, however, escalated its language against Israel, with President Abdel Fattah El-Sisi describing the country as "an enemy" in a fiery speech on Monday in Qatar during the Arab leaders' summit.

It was the first time an Egyptian leader had used the term since the two countries established diplomatic ties in 1979, said Diaa Rashwan, head of Egypt's State Information Service.

"Egypt is being threatened," Rashwan told the state-run Extra News television late Monday.

El-Sisi's remark comment played prominently across Egyptian newspapers' front pages on Tuesday through Cairo has taken no steps to change its formal diplomatic status with Israel.

Rubio spent about an hour meeting with Qatar's leader before heading back to the airport, where he was next scheduled to fly to the United Kingdom, where President Trump is set to arrive for an official state visit on Tuesday evening.

"We have a very short window of time in which a deal can happen" to end the war in Gaza, Rubio warned before arriving in Doha. "It's a key moment -- an important moment."

Rubio said "a negotiated settlement" still remained the best option, while acknowledging the dangers an intensified military campaign posed to Gaza.

"The only thing worse than a war is a protracted one that goes on forever and ever," Rubio said. "At some point, this has to end. At some point, Hamas has to be defanged, and we hope it can happen through a negotiation. But I think time, unfortunately, is running out."

Separately, a team of independent experts commissioned by the United Nations' Human Rights Council concluded that Israel is committing genocide in Gaza. It issued a report Tuesday that calls on the international community to end the genocide and take steps to punish those responsible for it.

Israel has refused to cooperate with the commission and has accused it and the HRC of anti-Israel bias. A statement from Israel's Foreign Ministry Tuesday says it "categorically rejects this distorted and false report."

Israel says Gaza City ground offensive against Hamas underway, as Rubio says time "running out" for peace deal