Fighters of Hamas, the group that rules Gaza, and its ally Palestinian Islamic Jihad (PIJ) jump out of tunnels to fire at incoming Israeli tanks, before slipping back into their vast underground network, residents said and videos from both groups showed on Thursday.

The guerrilla-style combat has forced Israel, which often utilises its powerful air force to hit Hamas hideouts from above, into a ground war as it seeks to overthrow the Palestinian group entirely.

The Israeli military on Thursday said it had lost the commander of its 53rd battalion in the fighting, bringing the total number of Israeli soldiers killed since it intensified its ground raid to 18.

The commander, Lieutenant-Colonel Salman Habaka, is believed to be the most senior Israeli officer killed since ground operations began in late October.

Israel said it had also killed dozens of Palestinian fighters in the offensive.

As the casualties grow, the war is also drawing closer to Gaza’s northern population hub, where Israel has ordered citizens to evacuate from or risk being seen as “terrorist accomplices”.

Israel has continued to pound the area with air raids, as military officials said they were amassing troops “at the gates of Gaza City”.

Hamas ‘well-prepared’

Israel acknowledged that Hamas was “well-prepared” for the battle, citing “minefields and booby traps” that were making access to the city difficult.

“This is certainly terrain that is more heavily sown than in the past with minefields and booby traps,” Brigadier-General Iddo Mizrahi, chief of Israel’s military engineers, told Army Radio. “Hamas has learned and prepared itself well,” he said.

Multiple axes

One Gaza City resident told Reuters news agency that Israel shelled the city all through Wednesday night but could not encroach city limits.

“In the morning, we [discovered] the Israeli forces are still outside the city, in the outskirts and that means the resistance is heavier than they expected,” said the resident, who asked not to be named.

Ejaz Haider, foreign affairs and military analyst, told Al Jazeera that the Israeli army is moving along multiple axes to surround where they assume Hamas fighters are.

“One idea could be, given how many reserves they have called up, to not just saturate the area with firepower, which they have done through the air and through artillery fire, but to also saturate the area with troops,” Haider told Al Jazeera.

“For Hamas, bringing them in is where they will be able to inflict maximum damage, at least in theory, on the incoming Israeli troops,” he added.

Attack on refugee camp

As Israel presses towards Gaza City, it has also carried out air attacks on the densely populated Jabalia refugee camp, claiming to target Hamas’s Qassam Brigades leaders hiding there.

Gaza’s authorities said at least 195 Palestinians were killed in the two hits on Tuesday and Wednesday, with at least 777 people injured and 120 others missing.

“It is a massacre,” said one person on the scene quoted by Reuters.

Israel said it had killed two Qassam Brigades leaders in Jabalia.

The latest war between Israel and Hamas broke out when the Palestinian group staged a surprise assault on Israeli territory. Israel says the group killed about 1,400 people, mostly civilians.

Israel’s ensuing bombardment of the enclave has killed more than 9,000 people, including more than 3,700 children, Gaza authorities say, while decimating the territory’s infrastructure and displacing hundreds of thousands.

Attacks ‘amount to war crimes’

The growing death toll and dire humanitarian conditions are drawing increased criticism from world leaders, activists, and international bodies.

The United Nations High Commissioner for Human Rights recently expressed concern that Israel’s “disproportionate attacks … could amount to war crimes”.

Even the United States, Israel’s staunchest ally that has offered unwavering support to it during the war and proposed a $14.3bn emergency aid package for its military, has begun to urge for caution.

“I think we need a pause,” said US President Joe Biden in a speech on Wednesday.

In a renewed diplomatic push, US Secretary of State Antony Blinken was on Thursday scheduled for his third visit to Israel since the war began.

Blinken plans to meet Prime Minister Benjamin Netanyahu on Friday to offer support, but also to drive home the need to protect civilians as much as possible, his spokesperson said.

Exit route for foreigners, wounded

After a total blockade of Gaza for more than three weeks, foreign passport holders and some severely wounded people were being allowed out as part of an Egypt-mediated deal.

Palestinian border official Wael Abu Mehsen said 400 foreign citizens would leave for Egypt via the Rafah crossing on Thursday after at least 320 people left Gaza on Wednesday.

Another 60 critically injured Palestinians would be crossing too, Mehsen added.

A woman waiting to pass through the Rafah border crossing told Al Jazeera that people in Gaza were “living in agony”.

“I need a response from any [Egyptian] official. I have been here since the day the crossing point was shelled weeks ago,” she said.

“I was scheduled to leave 20 days ago. That is too much; we are living in agony. We were all close to death,” she said, with her Egyptian passport in hand.