Israel delayed the release of over 600 Palestinian prisoners it had agreed to free, after Hamas handed over six Israeli hostages, over what the prime minister’s office said were repeated violations by the Palestinian group, Reuters reports.

Prime Minister Benjamin Netanyahu’s office said, hours after the Palestinians were to have been freed under an already fragile ceasefire deal, that the scheduled release would be delayed until the next release of Israeli hostages is secured “without humiliating ceremonies”.

The six hostages freed from Gaza were the last living Israeli captives slated for release under the first phase of a fragile ceasefire agreement that began last month.