Anti-austerity demonstrators in the German city of Frankfurt have set police cars alight and thrown stones in protest at the opening of a new base for the European Central Bank (ECB).

A police officer was hurt in the riot close to the Alte Oper concert hall.

Thousands of "Blockupy" activists are due to rally in the center of Frankfurt against the ECB's role in austerity measures in EU member states.

Police have set up a cordon of barbed wire outside the bank's new building.