Israel mounted it's attack in Gaza on Thursday and said it had attacked dozens of targets, leaving Palestinians struggling to survive in a situation the United Nations described as "apocalyptic."

Gazans crammed into Rafah on the border with Egypt, heeding Israeli leaflets and messages saying that they would be safe in the city. But medics and relatives said Israeli air strikes had killed 17 people in a house there on Wednesday sheltering some of those displaced from further north.

"The house was targeted by three rockets. They targeted women and children, as you can see, and the guests who were told the south would be safe," said Bassam al-Hobi, a member of the family that was hit, gesturing to bodies wrapped in white cloth, some small, lined up on the ground and surrounded by mourners.

As well as the 17 dead, three were missing and others wounded, he said. Elsewhere in Rafah, medics said four people had been killed while traveling in a rickshaw on Thursday.

Hamas-backed, al-Qassam Brigades, said combat was fierce after troops entered the heart of Khan Younis on Wednesday in a new phase of the war, which is now entering its third month.

Palestinian health officials said an Israeli airstrike had killed two people in Khan Younis on Thursday morning, while in central Gaza, medics said four people had been killed in a house in Nusseirat refugee camp overnight.

Those who escape violence face an increasingly desperate struggle to survive.

Hundreds of people packed a road in central city of Deir al-Balah, waiting for food outside a U.N. compound that had yet to open, a video posted by Ramy Abdu, founder of the Euro-Mediterranean Human Rights Monitor, showed.

The U.N. Palestinian Refugee Agency (UNRWA) said 1.9 million people – 85% of Gaza's population – had been displaced, its shelters were four times over capacity, and there was not enough aid to meet "the overwhelming needs."

The Palestinian death toll in the eight weeks of warfare reported by Gaza medics was at 16,015, including 43 reported by one hospital on Tuesday and 73 by another on Wednesday.

Gaza's Health Ministry has not released overall casualty figures since Monday, and it and the U.N. say hundreds of people are unaccounted for under rubble.

Bombing continues

Residents in Gaza City in the north reported all-night bombing and fierce gunbattles in Shejaia, east of the center, and the Jabalia refugee camp further north, where Qatar-based Al Jazeera Media Network said 22 relatives of its Gaza correspondent Moamen al-Sharafi had been killed.

Another district, Sabra, was also bombed, locals said.

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

"His home may not be his castle, and he can escape, but it's only a matter of time before we get him," he said.

Israel's move into Khan Younis followed a ground incursion into Gaza City in the north to root out Hamas and was accompanied by some of the heaviest bombing of the war.

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

The U.N. has been unable to distribute aid in every part of the Gaza Strip except for the Rafah governorate for the past four days, it said in its daily humanitarian report on Thursday.

In Rafah, about 13 kilometers (8 miles) south of Khan Younis, most of those displaced from elsewhere were sleeping rough as the U.N. had only managed to hand out a few hundred tents, the U.N. humanitarian office said on Wednesday.

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 hindering distribution, the report said.

Displaced civilians were also fleeing to the desolate area of al-Mawasi on Gaza's southern Mediterranean coast.

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

A Palestinian who fled there, Ibrahim Mahram, said five families were sharing a tent.

"We suffered from the war of cannons and escaped it to arrive at the war of starvation," he told Reuters. "We divide one tomato between all of us."

New cease-fire effort

Palestinian medics say Gaza's hospitals are overflowing with dead and wounded, many of them women and children, and supplies are running out.

Leaders of the Group of Seven nations, including Israel's close ally the United States, called for further humanitarian truces to address the humanitarian crisis and minimize civilian casualties.

A senior Hamas official told Reuters mediators were still exploring opportunities for a truce and reiterated its demand that Israel cease its attacks.

The U.N. Security Council received a UAE-drafted resolution on Wednesday demanding an "immediate humanitarian cease-fire," with a vote sought on Friday.