Israelis gathered across the country on Monday for the first national day of mourning since the Hamas-led Oct. 7 attacks, with protesters disrupting several ceremonies as they demanded that government ministers do more to secure the release of hostages.

Israel’s Memorial Day is normally one of the most somber on the country’s calendar, a date when Israelis put aside their differences to grieve fellow citizens killed in war or terrorist attacks. But the protests on Monday underscored how feelings of wartime unity have given way to deep disputes over the war in the Gaza Strip, the fate of hostages taken on Oct. 7 and domestic politics.

Critics heckled Prime Minister Benjamin Netanyahu as he attended a memorial at Mount Herzl in Jerusalem, the site of Israel’s national cemetery. One person was heard shouting, “Garbage.” Another said, “You took my children.”

At a ceremony in Ashdod, on the Mediterranean coast, bystanders shouted at the national security minister, Itamar Ben-Gvir, calling him a “criminal,” before his supporters tried to drown them out.

While the government has managed to secure the release of more than 100 hostages abducted by Hamas in the attacks, at least half of the roughly 240 people who were taken are either dead or still in captivity. Many of their loved ones want the government to agree to an immediate cease-fire with Hamas that would allow for the remaining captives to be released, even it means leaving Hamas in control of parts of Gaza.

The disruptions have precedent. Protesters taunted Mr. Ben-Gvir and other ministers last year, before the war began, when anger over the government’s efforts to overhaul the judicial system were the most prominent source of social division.

This year’s protests reflected growing anguish among parts of the population about the way Mr. Netanyahu’s right-wing coalition government has handled the war, causing enormous casualties and destruction.

Mr. Netanyahu has repeatedly pledged total victory over Hamas. But fighting across the Gaza Strip in recent days has underlined the notion that Hamas militants are still a force in the territory and might remain one for a long time to come. The pattern that has emerged in the war is that, after pitched battles, Israel’s military declares that it has taken control of an area and then moves on, only for Hamas fighters to return and reconstitute their forces.

On Monday, Israeli airstrikes shook the northern and southern ends of the territory, with the Israeli military saying it had struck more than 120 targets over the past 24 hours. Ground troops also engaged Hamas fighters in several locations, the Israeli military said. Amid the fighting, tens of thousands of fleeing civilians continued a desperate search for safety.

The fighting appeared to be heaviest in Gaza City, Beit Lahia and Jabaliya in northern Gaza, and in Rafah, the southern city where more than one million Palestinians had fled to try to escape Israel’s military offensive farther north. In recent days, hundreds of thousands have left Rafah, according to the United Nations.

Hamas said on Monday that it had launched mortars at Israeli soldiers near the Rafah crossing, which links Gaza and Egypt and has been closed since Israel seized it last week.

A spokesman for the United Nations said Monday that a U.N. staff member was killed Monday morning when a U.N. vehicle was struck on the way to a hospital in Rafah. Around 200 United Nations staff have been killed in the conflict.

Israeli society closed ranks behind the government and military immediately after the Hamas-led Oct. 7. But critics increasingly blame Mr. Netanyahu for failing to prevent the attacks, which the Israeli authorities say killed roughly 1,200 people, and for prolonging the war without winning the return of the hostages.

A poll conducted this month by the Israel Democracy Institute, a Jerusalem-based research group, suggests that a majority of Israelis see a hostage deal as a priority over a military operation in Rafah. Israeli officials call the city Hamas’s last major stronghold in Gaza, with battalions of fighters concealed there, but U.S. officials say that the group’s leaders in the territory are hiding in the city of Khan Younis, not Rafah.

Israel and Hamas have not agreed to a cease-fire and hostage release, despite months of mediation. And Mr. Netanyahu has insisted that Israeli forces will invade Rafah, with or without such a deal, amid threats by his far-right coalition partners to bring down the government if the war ends without the total defeat of Hamas.

On Monday at a Memorial Day ceremony in Holon, in central Israel, hecklers shouted at Miri Regev, the transportation minister, and called on her to resign. One asked: “What about the hostages?”

As Yoav Gallant, the defense minister, attended a ceremony in Tel Aviv, a protester held up a sign that said: “Their blood is on your hands.”

On Sunday night, Israeli peace activists broadcast their annual Joint Israeli-Palestinian Memorial Day Ceremony, with parallel events in London, New York and Los Angeles.

The ceremony is organized by Combatants for Peace and the Parents Circle-Families Forum, two peace-building organizations, and tries to recognize not only Israeli grief, but also the toll of Palestinian suffering over the decades.

The ceremony, held annually since 2006, was prerecorded this year to avoid the possibility of disruption by protesters. It featured speeches, songs, a poem about peace and a video that showed children in Israel and the Israeli-occupied West Bank talking about the effect of war.

Palestinians in the West Bank did not participate in person, given that Israel stopped allowing many Palestinians to work in Israel after the Oct. 7 attacks. There were also no direct contributions by speakers in Gaza.

More than 35,000 people have been killed in Gaza during Israeli’s military campaign to defeat Hamas, mostly children and women, health officials there say. Almost everyone in Gaza has been displaced from their homes amid a hunger crisis that aid workers say has been largely caused by Israeli restrictions on aid deliveries to the enclave.

The peace groups’ ceremony, which was screened at more than 200 venues in Israel, reflected the diversity and complexity of opinion within Israeli society about the war. Several speakers discussed their hope for an end to generations of bloodshed, and for peace.

Ghadir Hani read a contribution from a woman in Gaza, whose name was given only as Najla, describing how she had lost 20 family members in the war, including her brother, a father of two, who she said had been killed while going to look for food for his parents.

“They killed him while walking in the street though posing no threat whatsoever,” Ms. Hani read. “The death machine is still ready to kill,” she added. “But I know that on the other side there are many people who believe in peace.”

Liam Stack and Lauren Leatherby contributed reporting.