Hamas is set to free six more Israeli hostages Saturday from the Gaza Strip, but the exchange for hundreds of Palestinian prisoners is shadowed by heightened tension between the adversaries that clouds the future of the fragile ceasefire deal.

In what was set to be the largest swap under January’s ceasefire agreement, six hostages were freed, but the release of some 600 Palestinian prisoners was delayed. It comes after Shiri Bibas’s body was returned by Hamas.