The six Israelis were the last living captives set to be released in the first phase of the cease-fire. The agreement, strained for weeks, has an uncertain future.

The release of 620 Palestinian prisoners was delayed for several hours and was meant to occur after six Israeli hostages were released on Saturday.

Hamas on Sunday condemned Israel's decision to postpone the release of Palestinian prisoners and detainees, saying its claim that the hostages' handover ceremonies are "humiliating" was false and a pretext to evade Israel's obligations under the Gaza ceasefire agreement.

In a major shocker, Israel on Friday said, citing forensic reports that the Bibas brothers, whose corpses were returned by Hamas, were killed with "bare hands" by Hamas days after they were held captive in the Gaza Strip.