British Foreign Secretary Philip Hammond on Sunday demanded an unconditional ceasefire to resolve the "intolerable" situation in Gaza, adding that the British public was "deeply disturbed" by what it was seeing.
Hammond, who took over from William Hague last month, told the Sunday Telegraph that the killing had to stop, having already said he was "gravely concerned" by the number of civilian casualties from Israel's military operation in Gaza.
"The British public has a strong sense that the situation of the civilian population in Gaza is intolerable and must be addressed -- and we agree with them," he told the newspaper.
"It's a broad swathe of British public opinion that feels deeply disturbed by what it is seeing on its television screens," he added.
The former defence minister acknowledged the concerns of both Hamas and Israel, but insisted that they could not be allowed to stand in the way of a humanitarian ceasefire.
"We have to get the killing to stop," he told the paper.
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In a later statement, Hammond said he had spoken to Israeli Foreign Minister Avigdor Lieberman and Justice Minister Tzipi Livni by phone and commented on the shelling of a UN school where Palestinians were sheltering that killed 10 people.
"I am appalled at reports of further civilian casualties in the vicinity of a UN-run school housing Palestinians displaced by the Gaza conflict in Rafah this morning," Hammond said.
"The facts are not yet clear, but it is tragic that there are further losses of life in a place which is being used as a shelter."
He also welcomed signs that Israeli forces would withdraw from Gaza.
An Israeli army spokesman on Sunday told AFP that it had begun withdrawing some ground troops from the Gaza Strip and redeploying others, but operations against Hamas would continue.
The Israeli military campaign in Gaza has so far claimed more than 1,700 lives.
The office of British Prime Minister David Cameron on Saturday accused opposition Labour Party leader Ed Miliband of "playing politics" after he criticised Cameron's "silence" over Israel's actions.