Serbian premier Aleksandar Vucic was forced to flee a Sebrenica memorial Saturday when an angry crowd hurled stones at him at the 20th anniversary commemorations of Europe’s worst mass killing since World War II. Vucic had just laid a flower at a monument for thousands of victims identified and buried there when the crowd started to chant ‘Allahu Akbar'(God is Great) and hurled stones, forcing the prime minister to run for cover shielded by his bodyguards. Vucic, whose country backed Bosnian Serbs during and after the 1990s inter ethnic war in Bosnia, was among numerous dignitaries and tens of thousands of people attending the commemoration in the eastern town. Shortly before arriving, he condemned the “monstrous crime” in Sebrenica, where some 8,000 Muslim men and boys were murdered by Bosnian Serb forces who captured Sebrenica in July 1995, near the end of the war. Serbian and Bosnian Serb politicians have long denied the extent of the killing, although two international tribunals have described the bloodshed as a genocide.