JERUSALEM, Feb. 22 -- Hamas is set to release six more Israeli hostages from Gaza on Saturday, though the exchange for hundreds of Palestinian prisoners is overshadowed by heightened tensions that threaten the fragile ceasefire.

Israeli Prime Minister Benjamin Netanyahu vowed retaliation following what he called "a cruel and malicious violation" of the agreement, referring to the misidentification of a body released by Hamas.

Israeli forensic authorities confirmed that remains handed over overnight belonged to Shiri Bibas, a mother of two. Her body was released by militants on Friday after an earlier set of remains, initially believed to be hers, was later identified as an unknown Palestinian woman.

Three other bodies returned were con...