Protesters torched police cars and threw stones at officers during anti-austerity protests ahead of the inauguration ceremony for the European Central Bank's new headquarters in Frankfurt, Germany.
Police detained 350 people but said those intent on violence were a minority among the thousands who gathered to peacefully denounce government austerity policies.
Police said 14 officers suffered minor injuries, several from being hit with stones. A further 80 suffered from contact with some kind of irritating gas or liquid during the confrontations but recovered and later returned to duty.
The early morning violence quickly subsided. Some 10,000 people gathered later in the day for a peaceful rally on the Roemerberg, Frankfurt's main square.
The ECB ceremony went ahead, with ECB president Mario Draghi saying the new building was "a symbol of what Europe can achieve together". The ECB is the monetary authority for the 19 countries that have joined to share the euro currency.
The bulk of demonstrators conducted themselves peacefully, marching in groups, drumming and singing ahead. Some blocked bridges across the Main River or streets in an effort to hinder access to the ECB ceremony.
Leading activists distanced themselves from the violence. Ulrich Wilkens, a left-wing deputy in the regional parliament, said at news conference that he was "both depressed and horrified by what I experienced myself and saw in pictures".
The demonstrations were organised by Blockupy, an alliance including trade unions and anti-capitalist groups. Protesters said they were targeting the central bank because of its role in supervising efforts to restrain spending and reduce debt in financially troubled countries such as Greece.
At the ECB ceremony, Tarek Wazir, economy minister for the Hesse region, denounced the violence. He said the protesters "have no answers ... but they have some of the right questions", adding that "austerity can indeed be self-defeating".
He and several other German politicians including vice chancellor Sigmar Gabriel said the ECB was the wrong target.
Mr Draghi has urged more spending by governments that are in good financial shape such as Germany to help lift the economy and reduce unemployment. That advice has been ignored by the German government, which has stressed the need to balance its budget and pressed others to restrain spending.
The ECB, along with the European Commission and International Monetary Fund, is part of the so-called "troika" that monitors compliance with the conditions of bailout loans for Greece and other financially troubled countries in Europe.
Those conditions include spending cuts and reducing deficits, moves that are aimed at reducing debt but have also been blamed for high unemployment and slow growth.