Donald Tusk

Around half a million people have fled to Europe so far this year in search of sanctuary or jobs. As numbers swell, nations have tightened border security. Hungary has a razor-wire fence along its border with Serbia.

Countries in eastern Europe with little recent experience of migration are trading barbs over who is to blame, while Balkans neighbors Serbia and Croatia — who were at war in the early 1990s — issued threats and ultimatums.

Syriza's victory in Sunday's election marks a personal triumph for Tsipras, who served as prime minister between January and August — a tumultuous period that saw Greece's future in the 19-country eurozone come under real threat and strict banking controls imposed.

At 41, Tsipras dominates Greek politics despite a major policy U-turn that saw him go against the anti-austerity platform that swept him to power in elections in January in return for a multibillion bailout that keeps Greece in the eurozone.