"With heavy hearts, we, the members of the kibbutz, received the news this morning about the murder of our dear friend, Shlomo Mansour, 86 years old, who was kidnapped from his home in Kibbutz Kissufim during the Hamas terror attack on October 7, 2023," the community said of the Iraqi-born Israeli.

The Israeli military said in a statement on Tuesday that the "decision to confirm his death was based on intelligence gathered in recent months".

Israel's Defence Minister Israel Katz said in a post on X that Mansour had been "murdered in captivity" by Hamas on October 7.

One of the founders of Kibbutz Kissufim, Mansour was kidnapped from a henhouse during Hamas's attack on southern Israel.

His wife Mazal Mansour, with whom he lived for 60 years, managed to escape the attack. The couple have five children and 12 grandchildren.

The Israeli hostage forum said in a statement that Mansour, born in Baghdad, was a survivor of the Farhud pogrom -- a 1941 attack on Iraq's Jewish community -- and immigrated to Israel with his family at 13.

"This is one of the most difficult days in the history of our kibbutz," the community of Kissufim said in a statement.

"Shlomo was much more than a community member to us -- he was a father, grandfather, a true friend and the beating heart of Kissufim."

"Our hearts are broken that we couldn't bring him back to us alive".

The kibbutz called on the Israeli government and world leaders "to continue acting with determination to bring back all the hostages, both the living and the dead, and not to allow painful stories like Shlomo's to repeat themselves".

In a statement, Israeli Prime Minister Benjamin Netanyahu said that he and his wife, Sara, "share in the family's deep mourning".

"We will not rest and will not be silent until he is returned to a burial in Israel. We will continue to act with determination and without pause until we return all of our hostages - both the living and the fallen," he said.

A fragile ceasefire reached last month between Hamas and Israel appeared strained on Tuesday, a day after Hamas threatened to postpone the release of Israeli hostages scheduled for Saturday.

On Monday, US President Donald Trump warned that "all hell" would break loose if every Israeli hostage is not released from Gaza within the coming days, a threat Hamas said "further complicates matters."

The war in Gaza was triggered by the Hamas attack, the deadliest in Israel's history, which resulted in the deaths of 1,211 people, mostly civilians, according to an AFP tally of official Israeli figures.

Militants also took 251 hostages, of whom 73 remain in Gaza, including 35 that Israeli officials say are dead.

The health ministry in Hamas-run Gaza says the war has killed at least 48,208 people in the territory, figures which the UN considers reliable.