The mother of a 21-year-old man killed in Hamas's October 7 attack on Israel on Wednesday accused a United Nations worker of taking his body to Gaza.

Yonatan Samerano escaped the militants' bloody attack on the Nova music festival in the Negev desert, but was killed at nearby kibbutz Beeri.

The Israeli government has said a man seen on a video dragging Samerano's body into a white jeep was a social worker for the UN agency for Palestinian refugees (UNRWA).

Israel last month accused a number of UNRWA workers of taking part in the Hamas attack, prompting several countries to suspend funding to the agency and triggering two separate investigations.

At a news conference in Tel Aviv, Samerano's mother Ayelet called for the return of her son's body.

"How can social workers for an organisation that claims to promote good in this world do something so cruel and inhuman?" she asked.

"How can the UN pay this man who dragged my son's slim body on the ground and then picked him as if he was a prize to Gaza?"

Israel last week gave more details about the UNRWA staff members that it alleges were involved in the Hamas attack.

The man said to be in the video -- identified as 45-year-old Faisal Ali Mussalem al-Naami -- was described as a social worker for UNRWA but was allegedly also a Hamas commando.

He "was involved in kidnapping a soldier from Beeri (and) coordinated the transfer of weapons and trucks", the government said.

Others accused of involvement were said to be teachers or other staff members in UNRWA-run schools and health clinics.

Shelly Aviv Yeini, head of the legal team at the Hostages and Missing Families Forum, said the campaign group wanted "a comprehensive and transparent" probe into the claims.

"We seek assurances that the principle of neutrality, so vital to the UN's mission, is not just upheld, but is actively protected," she added.

UNRWA provides education and primary healthcare to Palestinians in Gaza, the West Bank, Jordan, Syria and Lebanon, employing some 30,000 people.

Israel's initial allegations against UNRWA saw the agency sack all those accused of involvement in the attack, in a bid to protect its wider reputation.

Two separate investigations -- one into the collaboration claims, the second about UNRWA's wider political neutrality -- are underway and due to report within weeks.

But since then, Israel has claimed Hamas tunnels were found directly under UNRWA's Gaza City headquarters, which it was forced to abandon as bombardments intensified in the Palestinian territory.