Thousands of Palestinians are fleeing northern parts of Gaza after Israel warned it was targeting the area in its campaign to stop rocket attacks.
The UN says 17,000 people have sought refuge in its facilities as Israeli air strikes continue for a sixth day. Israeli forces have raided a suspected rocket-launching site in Gaza in their first reported ground incursion.
At least 159 Palestinians have been killed since Israel's offensive began, according to health officials in Gaza.
The dead are said to include 17 members of one family who died in an Israeli missile strike on Saturday evening.
Israel says it is targeting Hamas militants and "terror sites", including the homes of senior operatives. However, the United Nations has estimated that 77% of the people killed in Gaza have been civilians.
The UN Security Council called for a ceasefire and peace talks on Saturday.