GAZA STRIP, Palestinian Territories -- Israel expanded its offensive against Hamas militants in besieged Gaza on Monday, as international concern deepened over the mounting civilian death toll in a war sparked by the Oct. 7 attacks.

The return to open warfare after the truce between Israel and Hamas expired has had ripple effects around a region on the cusp of a wider conflagration.

Since the expiry of the truce on Friday, fighting in Gaza has resumed between Hamas and advancing Israeli troops, as have launches of militant rockets toward Israel and Israeli air strikes on the Palestinian territory.

Over the weekend, Israeli air strikes on northern Gaza threw thick clouds of smoke and dust into the sky.

On Sunday, the Israeli army reported a string of rocket salvos from Gaza into Israel, adding that most had been intercepted.

The Hamas-run government in Gaza and the official Palestinian news agency, Wafa, said a strike had hit the entrance of the Kamal Adwan hospital in the north of the territory late Sunday.

Several people were killed in the strike, the news agency said, while Hamas accused Israel on Telegram of a "grave violation" of humanitarian law.

Contacted by Agence France-Presse, the Israeli military did not immediately comment on the alleged strike.

Israel says Hamas uses hospitals and other civilian infrastructure for military purposes -- an accusation that the militant group denies.

"The IDF continues to expand its ground operation against main Hamas fronts in the Gaza Strip," Israel military spokesperson Daniel Hagari said on Sunday. "Wherever there is a Hamas stronghold, the IDF operates," he said, referring to the Israel Defense Forces.

Israel has vowed to crush Hamas in retaliation for the militant group's Oct. 7 attacks that killed around 1,200 people, mostly civilians, according to Israeli authorities.

An estimated 240 others, among them young children and elderly people, were taken hostage into Gaza during the attacks.

The Hamas-run Health Ministry in Gaza says more than 15,500 people have been killed in the territory since Oct. 7, more than half of them women and children.

Under a truce mediated by Qatar with support from Egypt and the United States, 80 Israeli hostages were freed, in exchange for the release of 240 Palestinians held in Israeli jails.

More than two dozen other captives were also freed from Gaza.

However, fighting resumed between the two sides on Friday despite international calls for an extension.

The next day, Prime Minister Benjamin Netanyahu's office said Israeli negotiators were being withdrawn from Qatar "following the impasse in the negotiations" aimed at renewing the truce.

With 137 hostages still held in Gaza, according to the Israeli military, Hamas has ruled out more releases until a permanent ceasefire is agreed.

On Sunday, the Israeli military said it had carried out around 10,000 air strikes since the war started.

Israel on Sunday said two of its soldiers had died in combat, the first since the end of the truce.

"In the past few hours, only 316 dead and 664 injured people have been rescued from the rubble and taken to hospital, but many others are still stuck under the rubble," Hamas' Health Ministry spokesperson Ashraf al-Qudra said in a statement.

The mounting death toll in Gaza has sparked growing international concern over Israel's conduct of the war to eradicate Hamas.

On Sunday, hospitals in southern Gaza were overflowing with dead and wounded, some crying out in pain.

"I am running out of ways to describe the horrors hitting children here," James Elder, a spokesman for the United Nations children's agency UNICEF, said in a video from Nasser hospital in Khan Yunis.

"This is the worst bombardment of the war right now in south Gaza. I am seeing massive child casualties," he said in the video, posted on X, formerly Twitter.

Nine-year-old Huda, who was wounded in the head, arrived at the Deir al-Balah hospital with an International Committee of the Red Cross convoy bringing casualties from northern Gaza.

"She doesn't answer me any more," her father Abdelkarim Abu Warda said, sobbing.

Israel's ally the United States, which provides it with billions of dollars in military aid annually, has intensified calls for the protection of Gaza's civilians.

"Too many innocent Palestinians have been killed," Vice President Kamala Harris told reporters at UN climate talks in Dubai.

Israeli government spokesperson Eylon Levy said that the blame for the deaths lay with Hamas and those killed "would still be alive" had the group not carried out the Oct. 7 attacks.

With fears of a wider regional conflagration rising, a US destroyer shot down multiple drones over the Red Sea while assisting commercial ships in the Red Sea on Sunday, according to the US Central Command.

Yemen's Iran-backed Huthi rebels -- who said they targeted two of the ships -- launched a series of drones and missiles towards Israel in recent weeks and seized a cargo vessel last month, but the latest attacks mark a significant escalation in the threat to shipping in the area.

In Iraq, an air strike killed at least five pro-Iranian militants on Sunday, according to Iraqi security sources, a day after Baghdad warned Washington against "attacks" on its territory.

Fighting also flared on Israel's northern border with Lebanon.

The Israeli army said it had launched artillery strikes in response to cross-border fire, and its fighter jets hit a number of targets linked to Lebanese militant group Hezbollah.

Iran-backed Hezbollah said it had launched several attacks on Israeli positions, including a missile strike on a military vehicle. (AFP-Yonhap)