As the Gaza Strip crisis continued, almost 200 airstrikes were launched and 75,000 Israeli troops mobilised for a possible ground invasion. Tanks and artillery were positioned along the Gaza border.
The Israeli army said the strikes had zeroed in on a number of government buildings, including Prime Minister Ismail Haniyeh's office, the Hamas Interior Ministry and a police compound.
Gaza City was hit by a string of large explosions which began at around 3am yesterday and were followed by a fresh wave of strikes around two hours later.
Speaking about the operation in Gaza – dubbed the "Pillar of Defence" – Israeli interior minister Eli Yishai said: "The goal of the operation is to send Gaza back to the Middle Ages. Only then will Israel be calm for 40 years."
At least 43 Palestinians and three Israelis have died since Israel assassinated Hamas's military leader last Wednesday.
Palestinian militants have fired more than 100 rockets towards Israel, including two aimed at Tel Aviv. In the Israeli Mediterranean port of Ashdod, a rocket ripped into several balconies. Police said five people were hurt.
Major-General Tal Russo, commander of the Israeli forces on the Gaza frontier, said a ground operation was "definitely" possible.
Hen Kinan in Beersheba in Israel said: "There are still a lot of missiles coming into this area. I've counted at least nine salvos - and each time the alarm goes off it's not just one missile but several.
"We're not going out of the house, we're staying in the basement - My brother has two small children – they panic every time the air raid sirens go off.
"I don't want to see civilians killed on either side, but I support the fight against Hamas as a terror organisation."
Officials in Gaza said nearly half of the dead were civilians, including eight children and a pregnant woman.
Muhammad Abu Shaban, who lives with his family in Gaza City, said the situation is "terrible". He said: "We barely sleep for less than one hour daily, explosions are everywhere - People are really afraid."
Ahead of talks in Cairo between Hamas, Egypt, Qatar and Turkey aimed at brokering a ceasefire, Turkish Prime Minister Recep Tayyip Erdogan said that Israel must be "held to account" over what he called the "Gaza massacre".
He added: "Israel continues to make an international racket with its three dead. In fact, it is Israel that violated the ceasefire."
Arab League chief Nabil al-Arabi pledged to support the Palestinians against "Israel's aggression" and break the "siege" of Gaza.
Qatar is to give Egypt $10 million (about £6.3m) to help treat Palestinians wounded in Israeli air strikes in Gaza. Jordan's King Abdullah also ordered urgent humanitarian aid to be sent to Gaza "in view of the difficult circumstances in the face of Israeli aggression".
A senior Hamas source in Gaza said a proposal for a truce made by Turkey was being studied.
Tunisian foreign minister Rafik Abdessalem arrived in Gaza through the Rafah border crossing from Egypt to show support for Hamas. Later, he visited the wreckage of Hamas PM Ismail Haniyeh's HQ.
Abdessalem said: "Israel must realise that it is facing a changed Arab world that won't stand for what it is doing."
Mark Regev, an Israeli government spokesman, said: "We don't want to see any civilians caught up in the crossfire - But the simple fact is that Hamas has embedded - its military machine amongst the civilian population."
Hamas al-Aqsa brigades have also reportedly sent text messages to many Israelis, reading: "We will turn #Gaza into a cemetery for your soldiers."
Israeli police are reportedly planing a "sweep" for Palestinians illegally residing in Israel today, due to security concerns.
The White House said President Barack Obama was also in touch with the Egyptian and Turkish leaders. It is believed the Obama administration has been privately urging Israeli officials not to extend the conflict to a ground invasion, fearing this could play into the hands of Hamas and further damage Israel's standing in the region.
Publicly, the US has backed Israel solidly. Deputy national security adviser Ben Rhodes said that the White House believes Israel "has the right to defend itself" against attack and that the Israelis will make their own decisions about their "military tactics and operations".
UN Secretary-General Ban Ki-moon is expected to visit Israel and Egypt next week to push for an end to the fighting. Yesterday, UK shadow foreign secretary Douglas Alexander said efforts by Ban in the region within the coming days might be the only way to halt the violence.
Alexander said: "There must now be a full-scale diplomatic initiative, led by the UN Secretary-General himself, to try and bring this conflict to an end. The only hope for peace and security for the citizens of the region will be through re-starting the stalled negotiations towards agreeing a two-state solution."