By Lefteris Papadimas ATHENS (Reuters) - Mohammed Asif and his family have no food, no shelter and no security. Asif, who though 43 looks at least 20 years older, is one of thousands of Afghans trapped in Greece, their hopes of reaching sanctuary in northern Europe dashed by a cascade of border shutdowns from Austria to Macedonia. "What will we do now?" Most of the 400 Afghans vying for limited pavement space in Athens' Victoria Square are Hazaras, an ethnic minority who have long suffered discrimination and persecution back home, with thousands massacred by Taliban militias in the 1990s.