The UN says 17,000 people in Gaza have sought refuge in its shelters as violence continues for a seventh day.

Israel is to allow a pro-Palestinian activist group to sail two boats carrying humanitarian supplies into the Gaza Strip, after earlier hinting it would block the shipment from reaching the coastal territory.

Two boats filled with peace activists sailed toward Gaza today, bracing for a possible confrontation with Israel's navy as they try to reach the coastal strip in a symbolic attempt to break an international blockade of the territory.

After a four-month lull in fighting, the two largest Palestinian militant groups are threatening to withdraw from a cease-fire, accusing Israel of violating the truce with continued military operations.