May Day violence threatens to erupt in Berlin on Friday when far-right members, labour unions and leftists march in the capital against the backdrop of Germany's worst recession since World War Two.
The rioting on the May 1 Labour Day holiday that caused extensive damage to parts of the city starting in 1987 had been on the wane in the last three years after police shifted tactics from battling rioters to a pacifist policy of "de-escalation".
But the economic crisis, which has sent unemployment soaring and raised public ire over a growing disparity in wages, along with simmering anger over "gentrification" in some low-rent districts have raised police worries about this year's May Day.
Berlin Interior Minister Ehrhardt Koerting said there was indeed cause for concern: "The climate has become rougher. People are more emotional than a year ago because of the financial crisis," he told Der Tagesspiegel newspaper.
May Day is traditionally marked by union rallies in many European countries and the global economic downturn is expected to swell the crowds this year.
In France, the eight main unions have called for massive nationwide protests against President Nicolas Sarkozy's handling of the economy -- their third such day of action this year -- and a big union demonstration is also expected in Madrid, Spain.
But authorities are particularly concerned by the prospect of violence in Germany, especially in Berlin where the far-right NPD party plans a march that often draws violent counter protests from left-wing anarchists.
Several political leaders, including presidential candidate Gesine Schwan, have expressed fears the global economic crisis was creating an explosive atmosphere. Germany's gross domestic product will contract by a post-war record 6 percent in 2009.
Police have played down the spectre of an increase in May Day violence this year.
"There's a threat of violence, but it's nothing we haven't seen before," Berlin police spokesman Bernhard Schodrowski said.
Police unions however are concerned that the 5,000 police assigned to oversee a series of different demonstrations may not be enough. Unions have said another 4,000 police were needed.
"The stand-back policy in the past worked fairly well," said Rainer Wendt, a police union leader. "But there are reasons for worry. There will surely be violence. An internal police memo raised Berlin's alert level to the highest level of readiness."
The looming tensions in Berlin come against a backdrop of an increase in politically motivated crimes in Germany. Official statistics published in April showed an 11 percent rise in 2008.
Interior Minister Wolfgang Schaeuble has called the data "worrying", and said that "politically motivated crime appears to be more and more a product of a violent form of advocacy for ideological positions."