Israel's army on Monday sent dozens of tanks into southern Gaza as part of "aggressive" action against Hamas and its allies in the besieged territory, despite global concern over mounting civilian deaths.

Weeks after Israel deployed ground forces in the north of the Gaza Strip, the army has been air-dropping leaflets in parts of the south, telling Palestinians to flee to other areas.

Israel has vowed to crush Hamas in retaliation for the militant group's unprecedented October 7 attacks that killed about 1,200 people, mostly civilians, and saw around 240 hostages taken, according to Israeli authorities.

Gaza's Hamas-run health ministry says nearly 15,900 people have been killed in the Palestinian territory, about 70 percent of them women and children — a toll that has sparked global alarm and mass demonstrations.

Tanks, armored personnel carriers, and bulldozers were seen Monday near the southern city of Khan Yunis, which is crowded with internally displaced Palestinians, witnesses told AFP.

Amin Abu Hawli, 59, said the Israeli vehicles were two kilometers (1.2 miles) inside Gaza in the village of al-Qarara, while Moaz Mohammed, 34, said Israeli tanks were moving down the strip's main north-south highway, the Salah al-Din road.

The military was trying to cut the road between Deir al-Balah in central Gaza and Khan Yunis, "firing bullets and tank shells at cars and people trying to move through the area," Mohammed said.

The army said it was taking "aggressive" action against "Hamas and other terrorist organizations" in Khan Yunis.

The advance of Israeli forces meant that in the north and east of the city, civilians could no longer travel along the Salah al-Din road, which "constitutes a battlefield", the military warned. 

"It is extremely dangerous to go there."

Full-scale fighting resumed Friday after the collapse of a week-long truce brokered by Qatar with support from the United States and Egypt, during which Hamas and Israel had exchanged hostages and prisoners.

Trapped under rubble

Air strikes have since intensified in Gaza's south, said James Elder, a spokesman for the United Nations children's agency UNICEF.

"Despite what has been assured, attacks in the south of Gaza are every bit as vicious as what the north endured," he posted Monday on X, formerly Twitter.

"Somehow, it's getting worse for children and mothers."

Walaa Abu Libda found shelter at the Al-Aqsa hospital but said her four-year-old daughter remained trapped under rubble.

"I don't know if she is dead or alive," she said, one of an estimated 1.8 million people displaced in Gaza — roughly three-quarters of the population.

Israel's military said Sunday it had carried out around 10,000 air strikes in total, while more than 11,500 rockets had been fired at Israel since the war began, government spokesman Eylon Levy said.

The Israeli army said Monday that three more soldiers had been killed in fighting in the northern Gaza Strip, raising the number of troop deaths there to 75.

The fatalities brought to 401 the number of Israeli defense personnel killed since October 7, among them those killed in the Hamas attacks themselves.

Under the temporary truce that expired Friday, 80 Israeli hostages were freed, in exchange for the release of 240 Palestinians held in Israeli jails. More than two dozen Thai and other captives were also released from Gaza.

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

More air strikes have rained down on northern Gaza where Hamas's armed wing reported clashes with Israeli tanks.

Rocket salvos were again fired from Gaza towards Israeli territory.

'Like an earthquake'

In the southern Gazan city of Rafah, resident Abu Jahar al-Hajj said an air strike near his home felt "like an earthquake".

"The earth shook, and the sound was so loud. Pieces of concrete started falling on us," he said.

Israel's ally the United States has intensified calls for the protection of Gaza's civilians, with Vice President Kamala Harris saying that "too many innocent Palestinians have been killed".

A White House official said Sunday the United States believes Israel is "making an effort" to minimize civilian casualties in Gaza.

International Committee of the Red Cross president Mirjana Spoljaric, visiting Gaza, described the suffering as "intolerable".

Israel said that it was not seeking to force Palestinian civilians to permanently leave their homes.

"We have asked civilians to evacuate the battlefield and we have provided a designated humanitarian zone inside the Gaza Strip," military spokesman Jonathan Conricus said, referring to a tiny coastal area of the territory named Al-Mawasi.

Any suggestion of Palestinian dispersal is highly contentious in the Arab world as the war that led to Israel's creation 75 years ago gave rise to the exodus or forced displacement of 760,000 Palestinians.

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

Yemen's Iran-backed Huthi rebels said they had targeted two of the ships.

In Iraq, an air strike killed at least five pro-Iranian militants on Sunday, Iraqi security sources said, 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 targets linked to Iran-backed Lebanese militant group Hezbollah, a Hamas ally.

The Israel-occupied West Bank has also seen a surge in violence since October.

The Palestinian Authority's health ministry said two Palestinians had been shot dead in an Israeli raid on the northern West Bank town of Qalqilya, while a man was killed in Qalandia refugee camp.

Despite the war, Israeli Prime Minister Benjamin Netanyahu's corruption trial resumed on Monday. Netanyahu is accused of bribery, fraud and breach of trust, allegations he denies. The trial had been suspended after the October 7 attacks.