Violent clashes between between two groups of Eritreans, in which rioters threw stones, burned police cars and other vehicles, and badly damaged the event building took place in The Hague on Saturday evening, the police said. The violence was seen on television. The riot police were called in and used tear gas against the perpetrators. The mayor declared a state of emergency at the scene of the riots, giving the police more extensive powers. The number of those injured or arrested was not initially clear, police said. It was also not initially known what specifically triggered the clash. In re…