Militant group Hamas said on Thursday it was ready to begin talks on the second phase of a ceasefire in Gaza after several hundred Palestinians were released from Israeli jails overnight in return for the bodies of four Israeli hostages.

It was the final exchange of the six-week first phase of a ceasefire in Gaza that came into effect on Jan. 19.

Israel said on Thursday morning that three of the hostages whose bodies it had received overnight had been murdered in captivity, and the fourth had been killed on the day of the October 2023 Hamas raid into Israel that precipitated the war.

There was no immediate response from Hamas to the allegation the hostages had been killed in captivity. The group has previously denied killing hostages and said some had died as a result of Israeli bombardment.

Talks have yet to begin on a second phase of the ceasefire, meant to lead ultimately to a permanent end to the war which has destroyed much of the enclave.

Israel's government faces public pressure to stick to the ceasefire to free remaining hostages, while some within the right-wing government want to return to war to fulfill their objective of eradicating Hamas.

The dire condition of hostages handed over in recent weeks, including some who appeared emaciated and others including a baby that Israel says were murdered, have intensified public fury in Israel, potentially impacting talks to extend the truce.

Hamas said on Thursday the only way remaining hostages in Gaza would be freed is through commitment to the ceasefire.

"We renew our full commitment to the ceasefire agreement and confirm our readiness to enter into negotiations for the second phase of the agreement," the group said in a statement.

There are 54 hostages still held in Gaza. Israeli authorities believe fewer than half are still alive.

Israeli Energy Minister Eli Cohen told public broadcaster Kan that Israel demanded that the military stay the Philadelphi Corridor, which runs the length of Gaza's southern border with Egypt.

Israeli troops are supposed to start withdrawing from the Gaza-Egypt border area on Saturday, when the first phase of the ceasefire is set to end.

Israel and Hamas were supposed to start negotiations over the second phase of the agreement on the 16th day of the ceasefire, but there has been little indication of progress.

Cohen said Israel was in a stronger position to negotiate now than it was on the eve of the ceasefire because it has full backing from the U.S. administration of President Donald Trump, which this month began shipping heavy bombs.

Egyptian mediators on Wednesday secured the handover of the bodies of the final four hostages in the deal's first phase, in return for 620 Palestinians either detained by Israeli forces in Gaza or jailed in Israel. Israel had earlier refused to release prisoners on Saturday after Hamas handed over six hostages in a staged ceremony.

Hamas had been displaying living hostages and coffins holding hostage remains on stage in front of crowds in Gaza before handing them over, inciting criticism including from the United Nations. The final handover did not include such a ceremony.

President Isaac Herzog in a post on X confirmed the bodies received overnight were those of Tsachi Idan, Itzhak Elgarat, Ohad Yahalomi, and Shlomo Mantzur, all abducted during the Oct. 7, 2023, attack from their kibbutz homes near Gaza.

"In this painful moment, there is some solace in knowing that they will be laid to rest in dignity in Israel," he wrote.

Idan, Yahalomi, and Elgarat were murdered in captivity in Gaza, Prime Minister Benjamin Netanyahu's office said, while Mantzur was killed on Oct. 7, 2023, during the Hamas attack.

Hamas took 251 hostages and killed about 1,200 people in its October 2023 raid on southern Israeli communities, according to Israel. Around half of the hostages were freed during the war's only previous truce in November 2023, and others have been recovered alive or dead during the war.

At least 48,000 Palestinians have been killed in Israel's assault on Gaza, Palestinian authorities say. The war has laid waste to the crowded coastal enclave and displaced the majority of its population multiple times.

The Palestinians released overnight include 445 men and 24 women and minors detained in Gaza, as well as 151 prisoners serving life sentences for deadly attacks on Israelis, according to a Hamas source.

One bus transported detainees from Israel's Ofer prison in the occupied West Bank to Ramallah where cheering crowds had gathered to greet them.

Released prisoner Bilal Yassin, 42, told Reuters he had been in Israeli detention for 20 years.

"Our sacrifices and imprisonment were not in vain," Yassin said. "We had confidence in the (Palestinian) resistance."

Nearly 100 more Palestinian prisoners were handed over to Egypt where they will stay until another country accepts them, according to a Hamas source and Egyptian media.