Residents said tanks had reached the main north-south road through the middle of Khan Younis after intense combat through the night that had slowed the Israeli advance from the east. Warplanes were pounding the area west of the assault.
The air rumbled with the constant thud of explosions and thick columns of white smoke rose over the densely crowded city, filled with people displaced from elsewhere in the enclave.
Palestinians mourn relatives killed in the Israeli bombardment of the Gaza Strip in Khan Younis. (AP PHOTO)
As morning broke near a city-centre police station, the constant rattle of machine gun fire could be heard. Streets there were deserted apart from an old woman and a girl riding on a donkey cart.
"It was one of the most dreadful nights, the resistance was very strong, we could hear gunshots and explosions that didn't stop for hours," a father of four displaced from Gaza City and sheltering in Khan Younis told Reuters. He declined to be identified for fear of reprisals.
At the opposite end of the Gaza Strip, in northern areas where Israel had previously said its forces had largely completed their tasks, residents also described some of the most intense fighting of the war so far.
"I daresay it is the strongest battle we have heard in weeks," said Nasser, 59, a father of seven sheltering in Jabaliya after his house was destroyed in Beit Lahiya, another northern area. Explosions could be heard as he spoke.
"We are not going to leave Jabaliya regardless of everything. We shall die here as martyrs or they will leave us alone."
Israel vowed to annihilate Hamas, which has ruled Gaza since 2007, after militants burst across the fence on October 7 and went on a rampage through Israeli towns, gunning down families in their homes, killing 1200 people and seizing 240 hostages.
Since then, Gaza's health authorities say about 18,000 people have been confirmed killed and 49,500 injured in Israeli strikes, with thousands more missing and presumed dead under rubble. The toll no longer includes figures from northern parts of the enclave, beyond the reach of ambulances and where hospitals have ceased functioning.
Flames and smoke rise from Al Niusairat refugee camp after Israeli air strikes in south Gaza. (EPA PHOTO)
After weeks of fighting concentrated in the north, Israel launched its ground offensive in the south this week with a storm of Khan Younis. With combat now under way along nearly the entire length of the Gaza Strip, international aid organisations say its 2.3 million people have been left with nowhere to hide.
The World Health Organisation said it would be all but impossible to improve the "catastrophic" situation in Gaza, where medical needs had surged and the risk of disease grown while the health system had been greatly reduced.
The vast majority of Gaza's residents have now been forced from their homes, many fleeing several times with only the belongings they can carry. Israel says it is doing what it can to protect civilians, but even its closest ally the United States says it has fallen short of those promises.
An Israeli siege has cut off supplies, with the United Nations warning of mass hunger and disease.
Fighting between Israel and the Iran-backed Hezbollah movement in Lebanon, triggered by the Gaza conflict, intensified on Sunday.
At an international conference in Doha, capital of Qatar which acted as the main mediator for a week-long truce that saw more than 100 hostages freed, Arab foreign ministers criticised the United States for vetoing a UN Security Council resolution on Friday that demanded a humanitarian ceasefire in Gaza.
Qatar's Prime Minister Sheikh Mohammed bin Abdulrahman Al Thani said the war risked radicalising a generation across the Middle East. Jordan's foreign minister said the Israeli campaign aimed to drive Palestinians from Gaza and met the legal definition of genocide, accusations Israel called outrageous.
UN Secretary-General Antonio Guterres said he would "not give up" appealing for a ceasefire.
