Police in Germany are bracing themselves for further clashes after violence broke out in the early hours of May Day.Crowds are gathering in Berlin for marches. It is feared there could be a volatile mix of demonstrators – far right wing parties, labour unions and leftists are attending. Tension is already running high amid serious economic woes. Germany is suffering its worst recession since World War Two. Riots erupted overnight in Berlin and Hamburg and left dozens of police injured. Police unions have voiced concern that there will not be enough officers to patrol the crowds today. Some 5000 police are to be deployed – unions say thousands more officers are needed.