A dispute over humanitarian aid has led to concerns that the cease-fire could falter before the remaining hostages are released.

Israeli troops have withdrawn from the Netzarim Corridor - a military zone cutting off the north of the Gaza Strip from the south. Hundreds of Palestinians in cars and on carts laden with mattresses and other goods began returning to northern Gaza following the pull-out - often to scenes of utter destruction.

Under the ceasefire, Hamas has released 21 hostages in a series of exchanges for Palestinian prisoners. Prime Minister Benjamin Netanyahu has ordered the army to beef up troops in and around the Gaza Strip after Hamas threatened to call off a scheduled hostage release on Saturday, an Israeli official said.