Israeli tanks and troops pressed towards Gaza City on Thursday but met fierce resistance from Hamas militants using mortars and hit-and-run attacks from tunnels as the Palestinian death toll from nearly four weeks of bombardments mounted.

The war is closing in on the Gaza Strip's main population centre in the north where Israel has been telling people to evacuate as it vows to annihilate the Islamist group.

"We are at the gates of Gaza City," said Israeli military commander Brigadier General Itzik Cohen.

Fighters of Hamas and its ally Islamic Jihad were emerging from tunnels to fire at tanks, then disappearing back into the network, residents said and videos from both groups showed, in guerrilla-style operations against a far more powerful army.

"They never stopped bombing Gaza City all night, the house never stopped shaking," said one man living there, asking not to be identified by name. "But in the morning we discover the Israeli forces are still outside the city, in the outskirts and that means the resistance is heavier than they expected."

Aware of the difficulties of fighting in an urban environment, Israeli officers' strategy appears for now to be concentrating large forces in the northern Gaza Strip rather than launching a ground assault on the entire territory.

The latest war in the decades-old conflict began when Hamas fighters broke through the border on Oct. 7. Israel says they killed 1,400 people, mostly civilians, and took more than 200 hostages in the deadliest day of its 75-year history.

Israel's ensuing bombardment of the small Palestinian enclave of 2.3 million people has killed at least 8,796 people, including 3,648 children, according to Gaza health authorities.

Though Western nations and the United States in particular have traditionally supported Israel, harrowing images of bodies in the rubble and hellish conditions inside Gaza have triggered appeals for restraint and street protests around the world.

'HAMAS HAS PREPARED WELL'

Residents reported mortar fire around Gaza City and said Israeli tanks and bulldozers were sometimes driving over rubble and knocking down structures rather than using regular roads.

The south of Gaza was not spared either, with three Palestinians dead from tank shelling near the town of Khan Younis and an air strike killing five outside a U.N. school in Beach refugee camp, Gaza health officials said.

Brigadier General Iddo Mizrahi, chief of Israel's military engineers, said troops were in a first stage of opening access routes in Gaza but were encountering mines and booby-traps. "Hamas has learned and prepared itself well."

With Secretary of State Antony Blinken again en route to the region after saying the U.S. and others were looking at options for Gaza's future, Hamas blasted outside meddling.

"Our great Palestinian people and their valiant resistance will prevail over this fascist occupation," it added, demanding an independent state.

After a total blockade of Gaza for more than three weeks, foreign passport-holders and some wounded were allowed out at the southern end. Palestinian border official Wael Abu Mehsen said 400 foreign citizens would leave for Egypt via the Rafah crossing on Thursday, after some 320 on Wednesday.

Dozens of critically injured Palestinians were to cross too.

"I want to pass. We are not animals," said Ghada el-Saka, an Egyptian at Rafah waiting to return home after visiting relatives. "We've seen death with our own eyes," she added, describing a strike near her siblings' house that had made her and her daughter live on the street.

Israel's latest strikes have included the heavily-populated area of Jabalia set up as a refugee camp in 1948.

Gaza's Hamas-run media office said at least 195 Palestinians were killed in the two hits on Tuesday and Wednesday, with 120 missing and at least 777 people hurt.

Israel, which accuses Hamas of hiding behind civilians, said it killed two Hamas military leaders in Jabalia.

"We are fighting on all fronts and hitting Hamas wherever it is found," Israeli war cabinet minister Benny Gantz said, warning of a long and complex fight. "We will hunt them down through night and day, in their cities and in their beds."

With Arab nations vocal in their outrage at Israel's actions, the U.N. High Commissioner for Human Rights also expressed concern that Israel's "disproportionate attacks" may constitute war crimes.

Israel says it has lost 18 soldiers and killed dozens of militants since ground operations were expanded on Friday.

Violence has also spread to the occupied West Bank, with Israeli raids touching off confrontations with gunmen and people throwing stones.

Palestinian medics and the health ministry said three teenagers and a 25-year-old were killed there in clashes on Thursday. Israel's army had no immediate comment.

Separately, the military and medics said Palestinian gunmen killed an Israeli motorist in the West Bank.

HOSPITALS 'BEYOND CATASTROPHIC'

As international calls for a "humanitarian pause" in hostilities go unheeded, Palestinians are suffering shortages of food, fuel, drinking water and medicine. Sewage is leaking, some are drinking salt water and the trickle of aid permitted in by Israel is a tiny proportion of what is needed.

Hospitals, including Gaza's only cancer hospital, are struggling due to fuel shortages.

"The situation is beyond catastrophic in the hospitals in Gaza," said the charity Medical Aid for Palestinians, describing packed corridors, dwindling fuel, refugees in the courtyard and many medics themselves having lost homes and loved ones.

Ashraf Al-Qudra, a spokesperson for the Gaza health ministry, said the main power generator at the Indonesian Hospital was no longer functioning. The hospital was switching to a back-up generator but would no longer be able to power mortuary refrigerators and oxygen generators.

The United Arab Emirates offered to treat 1,000 children accompanied by families, while Turkey offered to take cancer patients from Gaza's Turkish-Palestinian Friendship hospital, which went out of service after running out of fuel.

(Reporting by Nidal al-Mughrabi in Gaza, Ali Sawafta in Ramallah, Dan Williams, Emily Rose, Maytaal Angel in Jerusalem, Clauda Tanios in Dubai; additional reporting by Reuters bureaux worldwide; Writing by Stephen Coates and Andrew Cawthorne; Editing by Angus MacSwan and Nick Macfie)