Four members of a Kurdish-led security force in northern Syria were killed Thursday morning in a Turkish drone strike, the area’s top military figure said, as Turkey steps up its threats to conduct a full-scale operation against Syrian Kurdish forces. The strike hit a vehicle carrying internal security force (Asayish) members in the town of Ain Issa near Raqqa as they drove to a camp for displaced persons in Tel Abyad, said Mazloum Abdi, commander-in-chief of the Syrian Democratic Forces (SDF). The Asayish named the four killed as Bashar Muhammad Ali Bozan, Jihan Mohammed Mustafa, Sarah Muhamm…