More than 300 airstrikes blighted the Gaza Strip on Saturday, with targets including a police compound and the prime minister's Hamas headquarters.
According to Israel's Haaretz newspaper, the state's Interior Minister Eli Yishai said on Saturday that the "goal of the operation is to send Gaza back to the Middle Ages."
Palestinian officials said that 12 had died in the Israeli attacks, which were launched in retaliation to more than 100 militant-fired rockets, which targeted Tel Aviv, Israel's largest city, following previous attacks on the city and on Jerusalem.
According to the Israeli military, a missile shield called "iron dome" knocked one of the Tel Aviv-bound rockets out of the sky, the defense system having already been deployed to great affect in the southern part of the state.
International leaders called for a cease-fire, with Egypt hosting leaders from Qatar, Turkey and Hamas in the hope of ending the violence.
According to the Associated Press, president Obama was in contact with the delegations in Cairo, however, US national security adviser Ben Rhodes reiterated the White House's position that Israel "has the right to defend itself".
On Saturday afternoon, protesters gathered outside the Israeli embassy in London to condemn the British Government's stance on the growing conflict.
With placards, flags and chants, the activists in London branded Israel a "terror state", claiming solidarity with the besieged people of the Palestinian enclave.
Organisers claimed that "thousands" of protesters had joined the rally, but reports suggest the number was much less.
Sarah Colborne, director of the Palestine Solidarity Campaign, said protesters wanted to show they were "vehemently opposed" to the Foreign Office's position.
She said: "We are insisting that the British Government uphold international law and human rights and tells Israel to end its war now.
"It's very clear what is happening here - Gaza is under siege, Israel started this by assassinating the person who was trying to negotiate a long-term truce with Israel.
"It's very clear who started this and who is suffering - 39 Palestinians have been killed so far and over 390 have been wounded.
"This war has to stop."
The crowds waved Palestinian flags, pounded drums and sang "Gaza we will never let you die" and "From London to Ramallah organise the intifada".
Throughout the afternoon more and more people joined the demonstration and lined both sides of Kensington High Street in front of the road leading to the embassy.
Manuel Hassassian, the Palestinian Authority's envoy to the UK, said: "At the popular level we have always been accustomed to see people supporting the Palestinian plight (in Britain).
"But we are very frustrated with the UK Government on its stand in supporting Israel in defending itself.
"How could an occupying force defend itself when they are occupying a land and putting 1.8 million Palestinians in a small strip under siege and blockade for five years?
"They have been living in an open air prison and the international community is watching the Israelis killing the Palestinians and inflicting so much damage on them and their properties without outright condemnation by these governments that claim to be democratic."
Hassassian said Israel was "digging its grave" and that the conflict heralded the "beginning of the end" for the Jewish state.
"The conflict is going towards convulsive violence, towards insecurity, towards de-stabilisation," he added.
Cars often honked their horns as they drove through the crowds, many of whom wore checkered Palestinian keffiyeh scarves.
Palestinian nationals mixed with members of Islamic organisations and supporters of groups such as the Stop The War coalition.
Commenting on why she was there, Kate Hudson, general secretary of the Campaign for Nuclear Disarmament, said: "Above all we want to make it clear that we deplore the approach of our Government, which is to stand aside and effectively condone what is taking place in Gaza today.
"Our own Prime Minister has described Gaza in the past as a prison camp so how can it be now that they stand aside and do nothing?"
On Saturday, the Israeli leadership called up 75,000 army reservists and stationed troops and tanks along the border in a clear signal that the government was contemplating a ground invasion into Gaza.
The move follows Prime Minister Benjamin Netanyahu's warning that his country is prepared to extend its operation against Hamas, sparking fears of a repeat of the ground incursion four years ago in which hundreds died.
Children's charity Unicef appealed for the "utmost restraint" from both sides to save more youngsters from death after six Palestinian children aged between 10 months and 15 years were killed by airstrikes.
On Saturday, Labour MP Douglas Alexander said it was time for the United Nations to get directly involved.
"What is needed now is an immediate end to the violence. We urge the UN Secretary General to visit the region this week to begin talks with all parties, and with partners in the region," he 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."
In a statement, Unicef said it was "deeply concerned about the deteriorating situation in Gaza and Israel and its impact on children.
"Both rocket attacks and airstrikes are putting children and their families at risk, leaving them exposed to physical harm and mental distress.
David Cameron and Foreign Secretary William Hague have urged both Israel and the Palestinians to make efforts to halt the violence.
But they made clear they thought Hamas bears the greatest responsibility for the current crisis, as well as the ability to bring it most swiftly to an end.