Palestinians in the Gaza Strip are living in "utter, deepening horror", the UN human rights chief said on Wednesday, as he pleaded for an immediate ceasefire between Israel and Hamas.
Volker Turk said there was a high risk of atrocity crimes being committed in such "catastrophic" humanitarian circumstances."
"Civilians in Gaza continue to be relentlessly bombarded by Israel and collectively punished - suffering death, siege, destruction and deprivation of the most essential human needs such as food, water, lifesaving medical supplies and other essentials on a massive scale," he told a press conference.
"Palestinians in Gaza are living in utter, deepening horror."
He said 1.9 million of the Palestinian enclave's 2.2 million people had been displaced and were being pushed into "ever-diminishing and extremely overcrowded places in southern Gaza, in unsanitary and unhealthy conditions".
"The catastrophic situation we see unfolding in the Gaza Strip was entirely foreseeable and preventable.
"As an immediate step, I call for an urgent cessation of hostilities and the release of all hostages," he said, adding: "you need to come back to your senses," he stressed.
Israeli forces on Wednesday were encircling southern Gaza's main city of Khan Younis, amid some of the most intense combat of its two-month-long war in the territory.
Israeli troops have shifted their brutal military campaign into the besieged territory's south following fierce fighting and bombardment that reduced much of the north to rubble and forced nearly two million people to flee their homes, causing a humanitarian catastrophe in Gaza.
Israeli tanks, armoured personnel carriers and bulldozers were seen on Tuesday near Khan Younis, forcing already displaced civilians to pack up and flee again, witnesses told AFP.
Many are faced with no choice but to flee towards Rafah, close to the Egyptian border.
The strikes come as the very few functioning hospitals in Gaza are overwhelmed, food is scarce and increased risks for people wishing to leave in search of safety.
The UNRWA agency warned that the territory is experiencing a new wave of displacement, stressing that there is no remaining "safe zone" in Gaza.
At least 16,248 Palestinians killed by Israel's deadly military campaign, including thousands of children, as of Wednesday.
The real death toll in the Strip is expected to be much higher than the reported one, because thousands of victims are trapped under rubble.
Deadly diseases are also spreading in the territory as a result of the bombing, siege, and complete collapse of healthcare infrastructure.