Israel's refusal to withdraw from a narrow strip of desert on the Gaza side of the border with Egypt, as called for in the ceasefire with Hamas, could further threaten the fragile truce. An Israeli official said Thursday that Israeli forces would remain in the so-called Philadelphi corridor to prevent weapons smuggling.

Hamas said Thursday it was ready to negotiate the next phase of the ceasefire in the Gaza Strip, after a swap in which it handed over what it said were the remains of four hostages in exchange for the release of more than 600 Palestinian prisoners held by Israel.

New tensions between Israel and Hamas are raising doubts about prospects for second phase of cease-fire and hostage deal in Gaza.