Islamic Hamas movement warned on Wednesday of a possible escalation of strikes by Israeli army against the Gaza Strip.In the meantime, Palestinian militants fired two more rockets into Sderot city of southern Israel.The cross-border violence between Palestinian militants and Israel renewed Tuesday, as the militants fired several projectiles from Hamas-controlled Gaza into southern Israel.Israeli airplanes responded with overnight raids targeting open spaces in Gaza, the first airstrikes since Egypt brokered a ceasefire that ended eight days of clashes between Hamas and Israel in November last year.The tension erupts anew after a Palestinian prisoner died of cancer at an Israeli hospital on Tuesday. The Palestinian officials accused Israel of delaying his treatment.Sami Abu Zuhri, a Hamas spokesman, said the Israeli air strikes last night were \"a outright violation\" of the ceasefire.He called on the international community \"to immediately intervene to bring an end to the Israeli escalation and to the violations against the prisoners.\"