Israeli troops and tanks backed by helicopter gunships have raided a refugee camp in the southern Gaza Strip, killing at least 14 Palestinians. The Israeli army says it was in response to “ceaseless Palestinian mortar attacks from Khan Younis at Israeli civilian targets.”Witnesses and medics said overnight air-raids killed seven people. Reports from Gaza say that at least four missiles were fired from an unmanned spy plane. One hit a post manned by Palestinian security men, killing two of them. After daybreak, troops opened fire on stone-throwers, killing five people including an 11-year-old boy. Tanks have bulldozed farmland and demolished houses in areas which, according to the Israeli army, were being used to launch mortars into Israel.