Blockupy is a left-wing political group protesting EU austerity policies, particularly those imposed recently on Greece.
"It was not what we had agreed upon or planned… I can fully understand the emotions of people who have been affected by the ECB's financial policies, but even if we protest against European policies, we still should behave like Europeans," Blockupy's Ulrich Wilken told journalists.
"Police made excessive use of special measures, such as tear gas and water cannons. According to our estimates, 10,000 police took part in the protest, equipped with 98 water cannons," Kleine said.
At least 16 protesters were arrested following the clashes to disrupt the opening of the new European Central Bank headquarters in the German city, police spokesperson Hesser Koschig told RIA Novosti.