Their remains were recovered Saturday "from an underground tunnel in the Rafah area" and returned to Israel where they were formally identified, the military said.

It said the dead hostages were Carmel Gat, Eden Yerushalmi, Hersh Goldberg-Polin, Alexander Lobanov, Almog Sarusi and Ori Danino, who were all seized by Palestinian militants during Hamas's October 7 attack on southern Israel that triggered the ongoing war.

Gat was taken from the southern Israeli kibbutz community of Beeri, while the remaining five, ages 23 to 32, were abducted from a music festival near the Gaza border.

They were among 251 people taken hostage during the October 7 attack, 97 of whom remain captive in Gaza including 33 the Israeli army says are dead.

Israeli Defence Minister Yoav Gallant said the six hostages whose remains had been retrieved were alive when taken captive.

"They were held hostage by Hamas and murdered in cold blood," Gallant said in a statement.

Military spokesman Rear Admiral Daniel Hagari said "they were brutally murdered by Hamas terrorists shortly before we reached them".

"The heart of an entire nation is shattered to pieces," President Isaac Herzog said in a statement.

"The blood of our brothers cries out to us. Our sisters and brothers are still there enduring hell... We have the sacred and urgent mission to bring them home."

Campaign group the Hostages and Missing Families Forum also insisted that the only way to bring the remaining hostages to Israel was a negotiated deal.

"A deal for the return of the hostages has been on the table for over two months," it said in a statement.

"Were it not for the delays, sabotage, and excuses those whose deaths we learned about this morning would likely still be alive."

The six dead hostages include four men and two women, and two with dual citizenship, Russian-Israeli Lobanov and Goldberg-Polin, who is also a US national and was seen alive in a video released by his captors in April.

Months long talks for a ceasefire and to secure the release of hostages have so far failed to have a positive outcome, with both Israel and Hamas blaming each other for the delays.

The October 7 Hamas attack resulted in the deaths of 1,205 people, mostly civilians, according to an AFP tally based on Israeli official figures.

Israel's offensive has so far killed at least 40,691 people in Gaza, according to the territory's health ministry. The UN rights office says most of the dead are women and children.

burs-ami-jd/hkb