Israel's army said on Saturday its troops recovered the body of a hostage abducted by Palestinian militants during the October 7 attack and later murdered in captivity in the Gaza Strip.

The recovery of Elad Katzir's body brings to 12 the number of bodies of hostages which the army says it has brought home from Gaza during the war.

But it gave no comfort to his sister, who blamed Israeli authorities for his death.

The Israeli army said in a statement that "the body of the abductee Elad Katzir, who according to intelligence was murdered in captivity by the Islamic Jihad terrorist organisation, was rescued overnight from Khan Yunis and returned to Israeli territory".

Katzir, 47 at the time of attack, was abducted from Nir Oz kibbutz community along with his mother Hanna.

She was released on November 24 during a one-week truce in the war in Gaza. Katzir's father was killed during the attack at the kibbutz, the army said.

The army said its intelligence suggested that Katzir was murdered in mid-January, shortly after Islamic Jihad released a video footage showing him in captivity.

"He was buried in the ground," a military official told journalists at a briefing.

Following intelligence, troops reached the site and "began excavation" work to recover his body, the official said.

"Their efforts resulted in the discovery of the body, which was then transported to Israel for further examination," he said.

Katzir's sister expressed fury at the authorities.

"Elad was kidnapped from his home in Nir Oz in one piece," Carmit Palty Katzir wrote on her Facebook page.

- 'Leadership is cowardly' -

She blamed the Israeli authorities for her brother's death, saying he would have returned alive had the authorities agreed to a new truce deal.

"Our leadership is cowardly and driven by political consideration, which is why this deal has not happened yet," she wrote.

"Prime Minister, war cabinet, and coalition members: Look at yourself in the mirror and say if your hands didn't spill blood."

Her comments reflect intensifying pressure on the coalition government of Prime Minister Benjamin Netanyahu over its handling of the war.

Negotiators were expected in Cairo over the weekend for a renewed push to strike a ceasefire-hostage deal as the war in Gaza reaches the six-month mark on Sunday.

Stop-start talks have made no headway since a week-long truce in November, the only one since the start of the war, saw the exchange of some hostages for Palestinian prisoners detained by Israel.

Campaign group The Hostages Families Forum said Katzir had been held alive for three months following his abduction.

During these months "signs of life and reports about his condition reached Israel," it said in a statement.

"Three months in which there was a possibility to save him and return him alive to his family and his country."

"The return of Elad Katzir's body is a painful, immediate, and harsh reminder that time has long run out for the hostages!"

- Polish citizen -

Yacov Livne, the Israeli ambassador to Warsaw, said on social media that Katzir had dual citizenship with Poland.

"Elad, from Kibbutz Nir Oz, is also a citizen of Poland... Alex Danzig, another Polish citizen from Nir Oz, is still held in Gaza," Livne said on X.

Poland's foreign ministry said on X that it "received the news with sadness" and expressed condolences.

Poland and Israel's ties have been strained by the Israeli strike in Gaza on Monday that killed seven aid workers, including Polish citizen Damian Sobol.

Poland has demanded a "criminal inquiry" into the killing.

Later on Saturday, in a separate statement released at a rally in Tel Aviv, the families of hostages again slammed the authorities for their handling of the hostage issue.

"For six months we have been in a nightmare that began on that cursed Saturday at 6:29 am, an ongoing nightmare that only gets worse from moment to moment," Esther Buchshtab, mother of hostage Yagev Buchshtab said.

"We demand that the state do everything to reach a deal, to bring back the living for rehabilitation and the murdered for burial."

The bloodiest-ever Gaza war began on October 7 with an unprecedented attack from Gaza by Hamas militants resulting in the death of 1,170 people in southern Israel, mostly civilians, Israeli figures show.

Vowing to destroy Hamas, Israel has relentlessly bombarded Gaza by air, land and sea, killing at least 33,137 people, mostly women and children, according to the health ministry in the Hamas-run territory.

About 250 Israelis and foreigners were taken hostage by militants on October 7.

Some 129 are still being held in Gaza, according to Israeli officials, including 34 who the army says are dead.