More than 500 Palestinians have been injured in the Israeli onslaught, which entered its third day Thursday, according to medical sources.
Ashraf al Qidra, a Palestinian health ministry spokesman, said two-thirds of the casualties were civilians, mostly women and children.
Al Qidra added that the number of civilian casualties had increased over the past 48 hours as the air force pounded residential areas and the coastline.
Three members of Islamic Jihad also died Thursday as their car was struck in Gaza, and a member of the Hamas Palestinian movement was killed in the north of the Strip, Israeli military sources said.
Israel's air and naval artillery forces have hit 108 targets overnight and 750 since the operation began, according to the Israeli Defence Forces (IDF).
The IDF said Palestinian militants had fired 360 rockets on Israel, 67 of which were intercepted by its Iron Dome missile defence system.
The al-Qassam Brigades, the Hamas's military wing, has claimed responsibility for the rocket attacks against Tel Aviv and other cities in central and southern Israel.
No casualties were reported in the Palestinian attacks, which activated alarm sirens again Thursday in Tel Aviv, but dozens of Israelis have been treated for anxiety and panic symptoms.
On Wednesday, Israel's Defence Minister, Moshe Ya'alon, vowed to increase attacks on Gaza.
"We will continue to hit Hamas and other terror groups in the Strip with heavy blows from the air, from the sea and from the ground so as to ensure the security of Israeli citizens," Ya'alon said, according to the online edition of Arutz Sheva.
Israel has been massing troops on the border with the Strip and has called up 40,000 reservists as it prepares to launch a ground offensive.
UN Secretary General Ban Ki-moon warned of the dangers of escalation and said the peace process was at stake, as the Security Council prepared to meet Thursday in an emergency session to discuss the situation.