A Palestinian civil defence team on Thursday called on the United Nations to investigate what it said were war crimes at a Gaza hospital, saying nearly 400 bodies were recovered from mass graves after Israeli soldiers departed the complex. "There are cases of field execution of some patients while undergoing surgeries and wearing surgical gowns at the Nasser Medical Complex," the civil defence forces said at a press conference, without presenting any evidence.

Palestinian authorities have this week reported finding hundreds of bodies in mass graves at Nasser hospital, the main medical facility in central Gaza, after Israeli troops pulled out of the city of Khan Younis.

Bodies were also reported to have been found at the Al Shifa hospital in northern Gaza, which was targeted in an Israeli special forces operation.

U.N. rights chief Volker Turk said on Tuesday he was "horrified" by the destruction of the Nasser and Al Shifa medical facilities and by the reports of the mass graves, according to a spokesperson.

The Israeli military said claims by Palestinian authorities that the Israeli Defence Forces (IDF) had buried the bodies were "baseless and unfounded".

It said forces searching for Israeli hostages had examined bodies previously buried by Palestinians near Nasser hospital and had returned them after they had been examined.

"The examination was conducted in a careful manner and exclusively in places where intelligence indicated the possible presence of hostages. The examination was carried out respectfully while maintaining the dignity of the deceased," it said in a statement.

Israel has denied killing those found in the graves and has released footage they say shows Palestinians digging these graves before the IDF operation.

The Palestinian Civil Defence Team accused Israel of burying a number of bodies in the Nasser complex in plastic bags at a depth of 3 metres (10 ft), where they quickly decomposed concealing evidence of its "crimes", including torture, it said.

The office of the prosecutor at the International Criminal Court in The Hague is investigating both sides in the Israeli-Gaza war, including the events of Oct. 7 and their aftermath.

Chief Prosecutor Karim Khan has said his team is "actively investigating any crimes allegedly committed" in Gaza and that "those who are in breach of the law will be held accountable".

(Writing by Michael Georgy; Editing by Sharon Singleton)