At least 30 missiles were fired by F-16 fighter bombers. The first round of airstrikes came just before noon, followed by several more waves of missiles, killing dozens and leaving many buried under the rubble. About 60 warplanes took part in the first wave of air strikes.
They were the heaviest Israeli attacks on Gaza for decades. More air raids were launched as night fell.
About 700 others were wounded, as missiles struck security compounds and other bases, said officials.
Residents spoke of children heading to and from school at the time of the attacks.
Palestinians staged demonstrations in the West Bank cities of Ramallah and Hebron, and there were some scuffles with Israeli troops there.
Egypt opened its border crossing to the Gaza Strip at Rafah to absorb and treat some of those injured in the south of the territory.
You can make a difference - Please help us help the Palestinians
Hadith - Sahih al-Bukhari 3.624, Narrated Anas, r.a.
Allah's Apostle said, "Help your brother, whether he is an oppressor or he is an oppressed one." People asked, "O Allah's Apostle! It is all right to help him if he is oppressed, but how should we help him if he is an oppressor?" The Prophet said, "By preventing him from oppressing others''.