The situation in Gaza City is nothing short of cataclysmic, a UN official has told the BBC, as Israeli tanks and troops continue to advance on the third day of a ground offensive.
Olga Cherevko, a spokeswoman for the UN's humanitarian office, said she had seen a constant stream of Palestinians heading south during a recent visit to the city, but that hundreds of thousands remained.
The World Health Organization (WHO) warned that overwhelmed hospitals were on the brink of collapse because it was being prevented from delivering lifesaving supplies.
The Israeli military said its forces were dismantling terror infrastructure and eliminating terrorists in Gaza City.
It has said its objectives are to free the hostages still held by Hamas and defeat up to 3,000 fighters in what it has described as the group's main stronghold.
However, the offensive on Gaza's biggest urban area, where one million people were living and a famine was confirmed last month, has drawn widespread international condemnation.
The UN and its humanitarian partners have recorded at least 200,000 people crossing from northern to southern Gaza since mid-August, when Israel announced its intention to conquer Gaza City. Around 55,000 have made the journey since Sunday.
Cherevko, who works for the UN humanitarian office in the central city of Deir al-Balah, told the BBC she travelled to Gaza City two days ago - a 29km (18 mile) round-trip that took 14 hours.
The things there, and the scenes on the way to Gaza City, are nothing short of cataclysmic, she recalled.
A constant stream of people [are] crossing from the north to the south, many on foot. Inside Gaza City, it's very crowded still because there are hundreds of thousands of civilians still remaining there.
She said she also witnessed multiple Israeli strikes very close to the UN convoy while in Gaza City, adding: It was really just a constant hit after hit while we were there.
On Thursday morning, witnesses told Reuters news agency they had seen Israeli tanks in the northern Sheikh Radwan neighbourhood and the southern neighbourhood of Tal al-Hawa, which have come under heavy bombardment in recent days.
Local hospitals said at least 14 people had been killed by Israeli fire across the Gaza Strip on Thursday, including nine in Gaza City.
Cherevko warned that many people were unable to comply with the Israeli military's order to evacuate to its designated humanitarian area in the south.
Hospitals, already overwhelmed, are on the brink of collapse as escalating violence blocks access and prevents the WHO from delivering lifesaving supplies.
The UN says there are currently about 1,790 in-patient hospital beds for the 2.1 million population of Gaza, resulting in occupancy rates of 180 to 300% across the 17 hospitals that remain partially functional across the territory.
The WHO's chief, Dr Tedros Adhanom Ghebreyesus, stated that the offensive is forcing traumatized families into an ever-shrinking area unfit for human dignity.
As this military operation continues, the humanitarian crisis in Gaza City appears to grow more severe by the hour, putting countless lives at risk.
