The head of the Gaza Strip's biggest hospital said on Monday after being freed from more than seven months of detention that he had been "tortured" by Israel.

Al-Shifa hospital director Mohammed Abu Salmiya was among more than 50 Palestinians released and returned to Gaza for treatment, according to an Israeli minister and a medical source in the besieged territory.

Salmiya said he was put through "severe torture" during his detention, which left him with a broken thumb.

"Prisoners are subjected to all kinds of torture," he told a press conference. "Several inmates died in interrogation centres and were deprived of food and medicine."

"For two months no prisoner ate more than a loaf of bread a day," said Salmiya.

"Detainees were subjected to physical and psychological humiliation."

The medical chief said no charge had ever been made against him.

Israeli forces detained Salmiya during one of a number of raids on Al-Shifa.

The hospital has largely been reduced to rubble by successive raids since Israel launched its assault on Gaza after the October 7 Hamas attacks.

Salmiya and the other freed detainees crossed back into Gaza from Israel just east of Khan Yunis, a medical source at the Al-Aqsa hospital in Deir al-Balah told AFP.

Five detainees were admitted to Al-Aqsa hospital and the others were sent to hospitals in Khan Yunis, the source added.

An AFP correspondent at Deir al-Balah saw some detainees in emotional reunions with their families.

Israel's military said it was "checking" reports about the release.

However, National Security Minister Itamar Ben Gvir confirmed the operation when he posted on X, formerly Twitter, that Salmiya's release "with dozens of other terrorists is security abandonment."

Israel's military has accused Hamas of using hospitals in the Gaza Strip as a cover for military operations. It has raided Al-Shifa and other hospitals, and says it has found tunnels and other infrastructure.

The militant group, which has run the territory since 2007, denies the allegations.

The Gaza European hospital in Khan Yunis said the head of its orthopaedic unit, Bassam Miqdad, was also among those freed on Monday.

In May, Palestinian rights groups said a senior Al-Shifa surgeon had died in an Israeli jail after being detained. The Israeli army said it was unaware of the death.

The war started with Hamas's October 7 attack which resulted in the deaths of 1,195 people, mostly civilians, according to an AFP tally based on Israeli figures.

Israel's retaliatory offensive has killed at least 37,877 people, also mostly civilians, according to data from the health ministry in Hamas-run Gaza. (AFP)