A mounting Israeli military advance on central Gaza on Thursday pushed tens of thousands of already displaced Palestinian families to take flight again in a new mass exodus.

Further south, Israeli forces struck the area around a hospital in the heart of Khan Younis, the Gaza Strip's main southern city, where residents feared a new ground push into territory crowded with families made homeless in 12 weeks of indiscriminate attacks.

Israel has escalated its ground war in Gaza sharply since just before Christmas despite public pleas from its closest ally the United States to scale the campaign down in the closing weeks of the year.

The main focus of fighting is now in central areas south of the wetlands that bisect the Strip, where Israeli forces have ordered civilians out as their tanks advance.

Tens of thousands of people fleeing the huge Nuseirat, Bureij and Maghazi districts of central Gaza were heading south or west Thursday into the already overwhelmed city of Deir al-Balah along the Mediterranean coast, crowding into hastily built camps of makeshift tents.

"Over 150,000 people – young children, women carrying babies, people with disabilities & the elderly – have nowhere to go," the main U.N. organisation operating in Gaza, UNRWA, said in a social media post decrying what it called "forced displacement" under Israeli evacuation orders.

The eastern part of Bureij was a theatre of heavy fighting on Thursday morning, with Israeli tanks pushing in from the north and east, residents and militants said.

"That moment has come, I wished it would never happen, but it seems displacement is a must," said Omar, 60, who said he had been forced to move with at least 35 family members.

"We are now in a tent in Deir al-Balah because of this brutal Israeli war," he told Reuters by phone, declining to give a second name for fear of reprisals. "Israel is killing doctors, social media influencers, journalists, and civilians."

Yamen Hamad, living in a school in Deir al-Balah since fleeing from the north, said the new refugees arriving from Bureij and Nuseirat were setting up tents wherever there was open ground. Some had fled areas where Israel had warned them to go, others had come without waiting to be told.

With food running out, he said he had made a perilous trip to Rafah near the Egyptian border to buy a 25-kilogram sack of flour for his family.

Fighting near hospital

Khan Younis, the main southern city where Israeli forces advanced this month after a truce collapse, came under heavy bombardment Thursday morning from warplanes and tanks near the Al-Amal hospital, west of Israeli positions.

The Palestinian Red Crescent, which runs the hospital and has its headquarters nearby, said 10 Palestinians were killed and 12 wounded in one bombardment there, the third strike targeting the area around the hospital in less than an hour.

Residents said they believed Israeli forces were trying to provoke a new exodus ahead of a further ground assault in the city. Al-Amal is not far from Nasser Hospital, the main hospital in Khan Younis and the largest still functioning in the enclave.

Palestinian officials reported 50 people killed in strikes in Khan Younis and in the central area. Israel reported three more of its soldiers killed in fighting in central and southern areas, bringing the toll in the ground campaign to 169. The past week has seen some of its heaviest losses of the war so far.

Israel says it will not halt its ground campaign in Gaza until it roots out the Palestinian resistance group Hamas for its Oct. 7 incursion that killed 1,140 people.

The Israeli assault in response has laid much of the enclave to waste, killing over 21,100 people – nearly 1% of Gaza's 2.3 million population – with thousands more dead feared lost in the ruins.

Virtually all residents have been driven from their homes at least once and many forced to flee several times. Only a handful of hospitals are still functioning.