Hamas is vowing to continue its fight against Israel from the Gaza Strip, despite more than 360 Palestinians being killed since the Israeli air attacks on the Gaza Strip began at the weekend.
More than 800 Palestinians have also been wounded.
The Israeli air offensive has gone into a fourth day, with raids on Hamas government buildings and security installations.
Israeli defence minister, Ehud Barak, says his country is involved in an all-out war against the Palestinian group and its leadership.
United Nations Secretary General, Ban Ki-moon, has called for an immediate stop to the violence. While recognising Israel's right to defend itself from militant rocket attacks, Mr Ban condemned its "excessive use of force".
Israel says its aim is to end the rocket attacks by Hamas-linked militants - of which there were reportedly more than 40 on Monday.
The United States - Israel's strongest ally - said the onus was on Hamas to end the violence and commit itself to a truce, but there have been angry protests against the offensive in many cities across the Arab world and in several European capitals.
The strikes began less than a week after the expiry of a six-month-long ceasefire deal with Hamas, which has controlled Gaza since 2007. Israel withdrew in 2005, but has kept tight control over access in and out of Gaza and its airspace.
An election is due to be held in Israel on 10 February.
Hostilities at sea
Meanwhile, an Israeli naval vessel has blocked pro-Palestinian activists trying to carry medical aid to Gaza by sea and escorted their boat back to Cyprus.
The two vessels collided during the incident, causing damage to both boats but no injuries. The activists said the naval vessel had rammed them after they ignored warning shots fired across their bow.
World leaders have called for Israel to keep open its border with Gaza to allow humanitarian supplies through to the territory's 1.5 million residents.
Egypt has allowed some trucks carrying aid to enter Gaza at the Rafah crossing, but a senior United Nations official says Israel's blockade means supplies of basic foodstuffs and medicines are dangerously low. He says 60 truckloads have been allowed in so far.
The Red Cross earlier described the situation in Gaza's hospitals as chaotic, with medical teams "stretched to the limit".
The UN says at least 62 of the Palestinians killed so far have been women and children.