More than 150,000 people have fled the Gazan city of Khan Younis since Monday, two UN agencies have said, the BBC reported.

Khan Younis, which is situated in the south of the Gaza Strip, has been the focus of a new Israeli military offensive.

The Israeli army issued an evacuation order for eastern parts of Khan Younis on Monday. It also reduced the size of the designated al-Mawasi humanitarian zone, which it claimed was being used by Hamas fighters to carry out attacks against Israel. 

At least 80 Palestinians have been killed in the area since the Israeli operation began, according to figures from Gaza’s Health Ministry.

An official from UNRWA - the United Nations agency for Palestinian refugees - told the BBC that an estimated 150,000 people had fled Khan Younis since Monday, when the latest evacuation order was announced.

"Over 80% of the Gaza Strip has been placed under evacuation orders or designated as no-go zones by the Israeli military," Louise Wateridge said.

On Tuesday, tanks were seen pushing deep into the Bani Suhaila district, with operations also taking place in the area of Al-Qarara.

Some residents attempted to flee to displacement camps in the eastern parts of Khan Younis, whilst others crammed into hospitals to seek refuge.

Rabah Abdul Ghafour, 37, a resident of Bani Suhaila, took shelter at Nasser Hospital.

“I have been displaced 12 times since 7 October,” he told the BBC. “We lived the hardest night of our lives. The sound of explosions and gunfire did not stop for a moment. It was as if the war had started yesterday.”

Rawan Al-Brim, 22, from Al-Qarara, arrived at Nasser Hospital with her husband and mother-in-law on Monday.

“We slept in the outer yard without a mattress or a blanket. My four-month-old daughter was born during the war. My breast milk has dried up and I can’t find any milk to satisfy her hunger. My baby screams from hunger all night,” she said.

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said it also assessed that 150,000 people had fled Khan Younis by monitoring population movements on the ground.

It said that many people were “trapped in the evacuation area,” including “people with reduced mobility and family members supporting them.”

“We’re seeing people moving to Deir al-Balah and western Khan Younis. Both of these areas are already extremely overcrowded,” Wateridge told the BBC. “They’ve got limited shelters and limited services available. They can barely accommodate the people who are already in these areas.”

In a statement, the Israel army said it had been operating "in the Khan Younis area over the past 24 hours".

Israel’s offensive comes as the World Health Organization said it was “extremely worried” about the possibility of an outbreak of the highly infectious polio virus in Gaza after traces were found in wastewater.