Israeli troops battled Hamas in the heart of south Gaza’s biggest city and said they had surrounded the militant leader’s house as thousands of displaced civilians sought shelter near Egypt and in a desolate seaside area of the enclave.

Gazans crammed into Rafah on the border with Egypt based on Israeli leaflets and messages saying that they would be safe in the city. But they remained fearful after an Israeli strike on a house there killed 15 on Wednesday, according to health officials in Rafah.

Israel’s military said it advanced into the heart of southern Gaza’s largest city, Khan Younis, for the first time. Hamas’ armed wing, the al-Qassam Brigades, said combat was fierce.

Residents said Israeli bombing grew more intense, killing and wounding civilians, and tanks battled Palestinian militants north and east of Khan Younis.

In “targeted raids” in central Khan Younis, Israel said its soldiers “eliminated terrorists, destroyed terrorist infrastructure and located weapons.”

Israeli Prime Minister Benjamin Netanyahu said Israeli forces encircled the Khan Younis house of Hamas leader Yahya Al-Sinwar.

“His house may not be his fortress and he can escape but it’s only a matter of time before we get him,” Netanyahu said in a video statement.

Khan Younis residents said Israeli tanks had neared Sinwar’s home but it was not known whether he was there. Israel has said it believes many Hamas leaders and fighters are holed up in underground tunnels.

Israeli warplanes also bombed targets across the densely populated coastal strip in one of the heaviest phases of the two-month-old war. WAFA, the official Palestinian news agency, said at least 17 were killed in an Israeli airstrike on a house in Maghazi in Central Gaza on Wednesday night

Qatar-based Al Jazeera Media Network said an Israeli bombardment of Jabalia Camp in northern Gaza killed 22 relatives of its Gaza correspondent Moamen Al-Sharafi, and it condemned the operation.

Hundreds of thousands of people made homeless in north Gaza during the war were desperately seeking shelter in the diminishing number of places in the south designated as safe by Israel.

The U.N. humanitarian office said in a report on Wednesday that most of the homeless people in Rafah, about 13 km (8 miles) south of Khan Younis, were sleeping rough due to a lack of tents although the U.N. had managed to distribute a few hundred.

The U.N. report said that while some aid had entered Gaza from Egypt through the Rafah crossing, the surge in hostilities since a week-long truce collapsed on Dec. 1 was hampering distribution.

Displaced civilians were also fleeing to the desolate area of Al Mawasi on Gaza’s southern Mediterranean coast, which Israel has said is safe.

The former Bedouin village lacks shelter, food and other necessities, according to refugee organisations.

“There are no bathrooms. We cannot even wash if we want to pray,” displaced Palestinian Enas Mosleh told Al Jazeera television. “It is a completely remote area.”

Another Palestinian who fled to Al Mawasi, Ibrahim Mahram, said five families were sharing a tent and he slept on a sidewalk.

“We suffered from the war of cannons and escaped it to arrive at the war of starvation,” he told the network.

“We divide one tomato between all of us.”

NEW CEASEFIRE EFFORT AT UN

Israel unleashed its military campaign in response to a surprise Oct. 7 incursion by Hamas fighters who rampaged through Israeli towns, killing 1,200 people and seizing 240 hostages, according to Israel’s tally.

Figures from Gaza’s Health Ministry put the death toll in Gaza at 16,015, including 43 reported by one hospital on Tuesday and 73 by another on Wednesday. But since Monday the ministry has not released daily casualty updates for all of Gaza, leaving it unclear whether the new overall toll was comprehensive.

As Israel broadened its ground onslaught on Wednesday after largely taking control of north Gaza last month, Palestinian medics said Gaza’s hospitals were overflowing with dead and wounded, many of them women and children, and supplies were running out.

In Geneva, the U.N. human rights chief said the situation was “apocalyptic” with the risk that serious rights violations were being committed by both sides.

Leaders of the Group of Seven nations including Israel’s close ally the United States called for further humanitarian truces “to address the deteriorating humanitarian crisis in Gaza and minimise civilian casualties”.

The United Nations Security Council received a UAE-drafted resolution on Wednesday that demanded an “immediate humanitarian ceasefire” with a vote sought on Friday.

Warning of a “severe risk of collapse of the humanitarian system,” United Nations Secretary-General Antonio Guterres on Wednesday invoked rarely used Article 99 of the founding U.N. Charter to push for a ceasefire in a letter to the Security Council.

The United States and its ally Israel oppose a ceasefire because they believe it would only benefit Hamas. Israel’s U.N. Ambassador Gilad Erdan denounced Guterres’ move: “The Secretary-General’s call for a ceasefire is a call to keep Hamas’ reign of terror in Gaza.”

The U.S. has called on Israel to do more to protect Palestinian civilians and increase the flow of aid to Gaza. Secretary of State Antony Blinken told CNN that Israel was taking some “important steps” such as designating safe areas and notifying neighbourhoods when civilians need to move.

“So that’s positive,” Blinken said.