KHAN YOUNIS, Gaza Strip/CAIRO, April 22 (Reuters) - Israeli troops fought their way back into an eastern section of Khan Younis in a surprise raid, residents said on Monday, sending people who had returned to abandoned homes in the ruins of the southern Gaza Strip's main city fleeing once more.

Elsewhere in Khan Younis, scores more bodies were recovered from what Palestinian authorities said were mass graves on the site of the city's main hospital, abandoned by Israeli troops. Further south there were fresh air strikes on Rafah, the last refuge where more than half of the enclave's 2.3 million people have sought shelter.

Israel abruptly pulled most of its ground troops out of the southern Gaza Strip this month after some of the most intense fighting of the seven-month-old war. Residents have begun making their way home to previously unaccessible neighbourhoods of what had been the enclave's second-biggest city, finding homes reduced to rubble and unrecovered dead in the streets.

"This morning many families who had left here in the past two weeks to go back home to Abassan came back. They were too frightened," Ahmed Rezik, 42, told Reuters from a school where he is sheltering in the western part of Khan Younis, referring to a district in the east.

"They said tanks pushed in the eastern area of the town under heavy fire, and they had to run for lives," he told Reuters via a chat app.

Israel launched its war in Gaza after fighters from the Hamas Islamist militant group that runs the enclave burst across the border fence on Oct. 7, killing 1,200 people and capturing more than 250 hostages, by Israeli tallies.

Israel responded by launching a ground assault on Gaza, vowing to annihilate Hamas. More than 34,000 people have since been confirmed killed according to Gaza health authorities, with thousands more bodies feared lost in the rubble.

'THE SCENE IS TOUGH'

In the ruins of what had been Nasser hospital, the biggest in southern Gaza, Reuters saw emergency workers in white hazmat suits digging corpses out of the ground with hand tools and a digger truck. The emergency services said 73 more bodies had been found at the site in the past day, raising the number found over the week to 283.

Israel says it was forced to battle inside hospitals because Hamas fighters operated there, which medical staff and Hamas deny.

Gaza authorities say the bodies recovered so far are from just one of at least three mass graves they have found at the site.

"We expect to find another 200 bodies at the same mass grave in the coming two days before we will begin working at the two other cemeteries," Ismail Al-Thawabta, director of the Hamas-run government media office, told Reuters.

He accused Israel of carrying out "executions" at the hospital and covering up the crimes by burying bodies with a bulldozer. Israel strongly denies having carried out executions.

Relatives have been coming to take away loved ones for reburial. Family members brought the body of Osama al-Shoubagy, one of those recovered inside the hospital grounds, to a graveyard on Monday to rebury him next to his sister, to whom he had once donated a kidney when she was sick.

"My young daughter asked me to visit the grave of her father. I would tell her that as soon as we bury him, we will visit him. Thank God. The scene is tough, but we might find some relief after burying him," said his wife Soumaya.

In one hand she held a few yellow flowers, in the other, the hand of their small daughter Hind, who wore a pale yellow Disney "Frozen" tracksuit to say goodbye to her father.

"He loved me, (and used to) buy things for me, and he used to take me out," the small girl said by the side of the new grave.

Gaza residents reported air strikes in several other areas, including Rafah, where a day earlier doctors had performed a caesarean section to save a baby from the womb of his mother who was among those killed.

In Nusseirat in central Gaza, officials said an air strike had damaged solar panels the hospital relies on for power.