Foreign secretary William Hague has condemned the violence in Israel and Gaza which has left 16 people dead but says that Hamas "bears principal responsibility for the current crisis".
Around 200 rockets have been fired by Palestinian militants into Israel from the Gaza Strip since a "surgical strike" by the IDF killed the Hamas top military commander, Ahmed Said Khalil al-Jabari, on Wednesday.
Three Israelis were killed when a rocket hit a four-storey-building in the southern Israeli town of Kiryat Malachi. A further two people were severely injured and two babies were also hurt.
Israeli airstrikes have killed 13 people, including an 11-month-year-old baby.
Hague said: "I utterly condemn rocket attacks from Gaza into southern Israel by Hamas and other armed groups.
"I am gravely concerned by the situation in Gaza and southern Israel and deeply regret the loss of civilian life on both sides. I call on all those involved to avoid any action which risks civilian casualties or escalates the crisis.
"Hamas bears principal responsibility for the current crisis. I utterly condemn rocket attacks from Gaza into southern Israel by Hamas and other armed groups. This creates an intolerable situation for Israeli civilians in southern Israel, who have the right to live without fear of attack from Gaza. The rocket attacks also risk worsening the plight of Palestinian civilians in Gaza, which is already precarious."
His comments were echoed by Douglas Alexander MP, shadow foreign secretary, who said: “The priority must be an immediate end to the violence to avoid a spiral downwards to even greater suffering. Escalating tension serves no one’s interest.
“This latest escalation of violence only emphasises why it is vital that negotiations to achieve a political solution to the Israeli-Palestinian conflict must resume with urgency.”
Earlier, Sir Mark Lyall Grant, the UK ambassador to the UN, called for a de-escalation of tension in the region to avoid a "spiral of violence".
Prime minister David Cameron will chair a meeting of the National Security Council on Thursday to discuss the crisis.