Heavy fighting raged overnight and into Sunday across Gaza, including in the devastated north, as Israel pressed ahead with its offensive after the U.S. blocked the latest international push for a cease-fire and rushed more munitions to its close ally.

Israel has faced rising international outrage and calls for a permanent cease-fire after the killing of thousands of Palestinian civilians. Nearly 85% of Gaza’s 2.3 million people have been displaced within the besieged territory, where U.N. agencies say there is no safe place to flee.

The United States has lent vital support to the offensive once again in recent days, by vetoing United Nations Security Council efforts to end the fighting that enjoyed wide international support, and by pushing through an emergency sale of over $100 million worth of tank ammunition to Israel.

Israeli Prime Minister Benjamin Netanyahu thanked U.S. President Joe Biden for the “important ammunition for the continuation of the war,” and for supporting Israel at the Security Council.

The U.S. has pledged unwavering support for Israel’s goal of crushing Hamas’ military and governing abilities, and returning all the hostages captured in the Oct. 7 attack that triggered the war.

Hamas and other Palestinian terrorists stormed into southern Israel that day, killing some 1,200 people and capturing around 240, over 100 of whom were released during a weeklong cease-fire late last month.

In response to the attack, Israel launched an air and ground war that has killed thousands of Palestinians, mostly civilians, and forced some 1.9 million people to flee their homes.

With only a trickle of aid allowed in, and delivery rendered impossible in much of the territory, Palestinians face severe shortages of food, water and other basic goods.

U.N. Secretary-General Antonio Guterres, who invoked a rarely-used power last week to call for a cease-fire, said “we are facing a severe risk of collapse of the humanitarian system.”

“The situation is fast deteriorating into a catastrophe with potentially irreversible implications for the Palestinians as a whole and for peace and security in the region,” he told a forum in Qatar.

Israel’s national security adviser, Tzachi Hanegbi, told Israel’s Channel 12 TV late Saturday that the U.S. has set no deadline for Israel to achieve its goals of dismantling Hamas and returning all the hostages.

“The evaluation that this can’t be measured in weeks is correct, and I’m not sure it can be measured in months,” he said.

Israeli forces continue to face heavy resistance, even in northern Gaza, where entire neighborhoods have been flattened by air strikes and where ground troops have been operating for over six weeks.

“The evaluation that this can’t be measured in weeks is correct, and I’m not sure it can be measured in months,” he said.

Israel’s Channel 13 TV broadcast footage showing dozens of detainees stripped to their underwear with their hands in the air.

Several held assault rifles above their heads, and one man could be seen slowly walking forward and placing a gun on the ground before returning to the group.

Other videos in recent days have shown groups of unarmed men held in similar conditions, without clothes, bound and blindfolded.

Detainees from a separate group who were released Saturday told The Associated Press they had been beaten and denied food and water.

Israel has not commented on the latest video or the allegations of mistreatment, but government spokesman Eylon Levy said “increasing numbers” of Hamas fighters were surrendering and handing over their weapons, calling it a sign of “collapsing” morale.

Residents said there was still heavy fighting underway in the Gaza City neighborhood of Shijaiyah and the Jabaliya refugee camp, a dense urban area housing Palestinian families who fled or were driven out of what is now Israel during the 1948 war surrounding its creation.

“They are attacking anything that moves,” said Hamza Abu Fatouh, a resident of Shijaiyah. He said the dead and wounded were left in the streets as ambulances could no longer reach the area, where Israeli snipers and tanks had positioned themselves among the abandoned buildings.