Israel's military confirmed Wednesday that a hostage kidnapped in the 7 October Hamas attack was killed during a failed army rescue operation in December in the Gaza Strip.

Sahar Baruch, among 250 hostages seized by Palestinian militants and taken to Gaza after the shock attack on southern Israel, was confirmed dead last month by his kibbutz community.

The army said it had notified Baruch's family that he was killed during "an attempt to rescue him on 8 December."

"At this stage, we are unable to determine the circumstances around his death and whether he was killed by (Israeli) fire or he was murdered by Hamas," the army said in a statement.

Hamas announced Baruch's death on 9 December, saying he was killed during an attempt by the army to rescue him and released a video showing his remains.

The Hamas attack on Israel resulted in the deaths of around 1,140 people, most of them civilians, according to an Agence France-Presse tally based on official Israeli figures.

Among the hostages taken to Gaza, some 129 still remain in captivity, according to Israel.

In response to the deadliest attack in its history, Israel launched a relentless offensive that has reduced vast swathes of Gaza to rubble and claimed over 22,300 lives, according to the territory's health ministry.