Israeli forces clashed with Hamas militants across the Gaza Strip on Saturday, the Israeli military said, deepening its engagement in the decimated enclave even as the Palestinian death toll from relentless airstrikes in 12 weeks of war soared higher.

The Gaza Health Ministry reported Saturday that 165 people had been killed in Israeli airstrikes and artillery attacks in the previous 24 hours, adding to the toll of more than 20,000 people killed in Gaza since the war began with the Oct. 7 Hamas-led raids into Israel.

The Israeli military said late Friday that it had destroyed a Gaza City apartment of the person it considers the mastermind of those attacks, Yahya Sinwar, the Hamas leader who sits atop the list of the Israel military’s most-wanted list in Gaza.

The army said Mr. Sinwar used the apartment as a hide-out and that it destroyed a tunnel shaft discovered by its troops in the apartment’s basement floor, as well as an underground headquarters that served as a nerve center for senior officials from Hamas’s military and political wings.

He was not believed to be in the complex when it was hit, having decamped to the south when the Israeli campaign began.

As global outrage and impatience grows with the war’s devastating human toll, the Biden administration said late Friday that it was bypassing Congress for the second time since the war started for a weapons sale to Israel.

The State Department approved a proposed $147.5 million sale of artillery munitions and related equipment to Israel, invoking an emergency provision that avoids a congressional review process generally required for arms sales to other nations, the Biden administration said. The department used the same provision this month to facilitate a government sale of about 13,000 rounds of tank ammunition to Israel.

The Pentagon said in a statement that Secretary of State Antony J. Blinken had “provided detailed justification to Congress that an emergency exists that requires the immediate sale” to Israel.

“The United States is committed to the security of Israel, and it is vital to U.S. national interests to assist Israel to develop and maintain a strong and ready self-defense capability,” the statement said, adding: “It is incumbent on all countries to employ munitions consistent with international humanitarian law.”

Hamas said in a statement Saturday that the U.S. provision of ammunition to Israel was “clear evidence of the American administration’s full sponsorship of this criminal war.”

The Israeli prime minister, Benjamin Netanyahu, is facing increasing pressure from the United States and many other nations to lower the conflict’s intensity, but he said last week that Israel would be “deepening” the fighting in coming days.

At a televised news conference on Saturday, Mr. Netanyahu vowed again that Israel would not stop its campaign until it achieved victory, and said that the war would continue for “many more months.”

Israeli airstrikes and artillery pounded central and southern Gaza on Saturday, striking areas where hundreds of thousands of displaced civilians were told by Israel to congregate for safety from the onslaught across the territory, according to the Palestinian news media.

Israel says it has killed thousands of Hamas militants, including several commanders, but it has failed to locate Mr. Sinwar, whose killing or capture would be a significant blow to Hamas. Israel,has offered $400,000 to anyone who can provide information leading to his arrest.

A founding member of Hamas in the 1980s, Mr. Sinwar spent decades in Israeli prisons after being arrested in 1988 and convicted of murdering four Palestinians who were suspected of collaborating with Israel.

Despite having received a life sentence, he was released in 2011 as one of the 1,026 Palestinians freed from Israeli jails in exchange for the release of an Israeli soldier, Gilad Shalit, whom Hamas had abducted five years earlier. Upon Mr. Sinwar’s release, he committed himself to obtaining the release of other Palestinians incarcerated in Israel.

The army statement on Friday described the underground headquarters connected to Mr. Sinwar’s apartment as part of a network of tunnels “in which senior officials of the Hamas terrorist organization moved and operated.”

The headquarters was described as about 20 yards underground, which Israel said was deeper than other tunnels. The army said it had ventilation and electricity, and was linked to sewage lines. It led to a tunnel about 250 yards long that the army said contained rooms for prayers and for resting, and stocked for an extended hide-out.

“The tunnel was built so that it would be possible to stay inside it and conduct combat from it for long periods of time,” the army statement said.

Hamas’s top leaders are believed to be sheltering in deep tunnels under Gaza along with most of the group’s fighters and the remaining hostages abducted in the Oct. 7 attacks. Although the Israeli army says it has demolished at least 1,500 shafts, experts believe the underground infrastructure to be largely intact.

Israel’s search-and-destroy missions and its intensive bombardments have come at the cost of thousands of women, children and other noncombatants killed.

Unverified video footage from local journalists in the southern Gaza city of Rafah, where large numbers of displaced people have fled, showed the immediate aftermath of strikes on residential homes. In chaotic scenes in narrow crowded streets, people carried the injured out from the rubble, wrapped in blankets. Other wounded were ferried by hand, as several men struggled to carry a man’s limp body.

Israeli airstrikes also hit parts of central Gaza that were under Israeli evacuation orders issued this week. More than 150,000 people are affected by those orders, according to the United Nations, though it was unclear how many have fled. The strikes forced some families who have already been uprooted numerous times into yet more difficult decisions about whether to move again.

A strike on the home of a journalist in the central Gaza town of Nuseirat killed him and a number of his family members and injured several others, according to Palestinian media.

More journalists have been killed in the 12 weeks of the Gaza war than have ever been killed in a single country over an entire year, according to the Committee to Protect Journalists, which calculates that at least 69 journalists and media workers had been killed since Oct. 7.

Matt Surman and Edward Wong contributed reporting.