The Israeli military warned on Friday that it was stepping up operations in the southern Gaza Strip, where hundreds of thousands of people had fled to safety, while hospital officials said Israel bombed an area in the south where it had ordered civilians to seek shelter.

At least 18 people were killed and dozens of others injured near Kuwait Specialty Hospital, according to hospital staff members, who said the strike had hit a house in Rafah, near the border with Egypt.

In what an Israeli defense official described as an “essential” stage in the war to eliminate Hamas, the military carried out a series of attacks over the past day in Khan Younis, the biggest city in south Gaza, using airstrikes, sniper fire and tank rounds.

Yoav Gallant, Israel’s defense minister, called the strikes an important part of the mission to destroy the militant group and its weapons caches.

“Our operations are essential to achieving the goals of the war,” he said. “We see the results and the destruction of enemy forces.”

Palestinian health officials said that scores of civilians had died in the raids, while a United Nations official said that Israeli forces shot at a U.N. convoy of armored vehicles on Thursday evening as it was returning from an aid mission in the northern part of the territory.

No one in the convoy was injured, the official said, but the episode highlighted the severe challenges facing humanitarian efforts to help Palestinians struggling to survive amid Israel’s nearly 12-week bombardment of the enclave.

“Israeli soldiers fired at an aid convoy as it returned from northern Gaza along a route designated by the Israeli Army,” Thomas White, the Gaza director for UNRWA, the U.N. relief agency for Palestinian refugees, wrote on social media. He said that one vehicle in the convoy had been damaged, adding: “Aid workers should never be a target.”

Amid widespread calls for a cease-fire and outrage over the more than 20,000 people Gazan officials said have been killed in the war, the International Court of Justice said on Friday that South Africa had filed an application to begin proceedings against Israel for what it said were acts in Gaza that were “genocidal in character.”

A news release by the court said the complaint accused Israel of trying “to destroy Palestinians in Gaza as a part of the broader Palestinian national, racial and ethnical group.”

Israel’s Foreign Ministry said on Friday that it “rejects with disgust the blood libel spread by South Africa,” and said Hamas was responsible for the suffering of the Palestinians by using them as human shields.

“Israel has made it clear that the residents of the Gaza Strip are not the enemy, and is making every effort to limit harm to the non-involved and to allow humanitarian aid to enter the Gaza Strip,” the statement said.

The Israeli military in recent days has issued rare admissions of fault over its conduct of the war.

On Thursday, it said it had caused “unintended harm” to “uninvolved civilians” in two strikes this week on a densely packed neighborhood in the Gaza Strip.

And in findings released on Thursday, the military said the mistaken killing of three Israeli hostages this month “could have been prevented” but added that the military’s operations in the area had been “carried out under complex circumstances, and in intense combat conditions under a prolonged threat.”

Israeli forces are moving into the community of Khirbat Ikhza’a in southern Gaza, the military said on Friday, just over the border from Nir Oz, a kibbutz that was one of many southern Israeli communities that Hamas targeted during the deadly Oct. 7 attacks that Israeli officials said killed 1,200 people.

Israeli troops are “working to gain operational control of the Khirbat Ikhza’a area,” the military said, releasing footage of troops running past the rubble of destroyed homes and taking positions among backyard citrus trees in what were residential neighborhoods before the war.

Saying that “dozens of terrorists” had been killed in central and southern Gaza, the military posted videos of airstrikes and images of a soldier piloting a drone into a tunnel shaft. Other photos showed munitions and military uniforms that Israeli forces say they had found in abandoned homes, articles that were juxtaposed with household appliances.

At the same time, news photographers in Gaza captured the devastating human toll of the conflict: a wounded child on an operating table, arms limp and covered with dust, as he was jostled by medical staff wearing bloodstained latex gloves; an injured woman buried in rubble, her face half covered in fresh blood as men frantically tried to extract her; a man and woman outside a hospital, disheveled and with their faces contorted in grief.

About 85 percent of Gaza’s 2.3 million people have been displaced, and those sheltering in the south have hardly anywhere to go. The Kuwait hospital is less than a mile from Gaza’s border with Egypt, which Egypt is determined to keep closed.

The city’s border crossing with Egypt is also the main entry point for aid into the territory, but Israel has continued to conduct military operations in the area, hampering aid efforts for residents growing increasingly desperate for food and other vital supplies.

After Thursday’s strike, many who arrived at the Kuwait hospital had serious injuries, including head wounds and severed limbs, the hospital’s director, Dr. Suhaib Al Hams, said in a video on social media.

News photos from the scene of the strike showed people pulling young children from the rubble. In one image, a girl in colorful pajamas appeared limp as she was carried away.

An Al Jazeera correspondent who saw the strike and visited the hospital in the immediate aftermath, Tareq Abu Azzoum, reported that it had destroyed a residential building.

Nesreen Joudeh, who has been sheltering with 29 members of her extended family in a two-bedroom apartment in Rafah, told The New York Times in text messages that strikes on Thursday night “were very intense, loud and close.” She said, “We are all terrified.”

Airstrikes hit near the apartment, and the blasts smashed the windows, she said. The apartment was already cold for Ms. Joudeh, 38, and her family, who have been sleeping on the floor with no winter clothes or blankets.

If Israeli ground forces move into Rafah, she said, they wouldn’t know where to go.

“It is supposed to be safe, but no place is safe in Gaza,” she said.

Raja Abdulrahim and Abu Bakr Bashir contributed reporting.