Thousands of anti-capitalist protesters clashed with riot police near the new headquarters of the European Central Bank (ECB) in Frankfurt, hours before the ceremonial opening of the €1.3bn (£934m, $1.4bn) building.

Police cars were set on fire and streets were blocked by stacks of burning tyres and rubbish bins.

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Four police cars burn after being set on fire by anti-capitalist protesters near the European Central Bank (ECB) building in Frankfurt, hours before its official openingKai Pfaffenbach/Reuters
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Police detain an anti-capitalist protester near the European Central Bank (ECB) buildingKai Pfaffenbach/Reuters
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A German police officer who was hit by a paint bomb thrown by anti-capitalist protesters looks at a burning police carKai Pfaffenbach/Reuters

Several thousand riot officers pursued what they said was a minority of violence-minded activists as the bulk of protesters conducted themselves peacefully ahead of a rally in the city's main square. Some blocked bridges across the Main River or streets.

The organisers of the protest, a group called Blockupy – named after the Occupy Wall Street movement in 2011 – estimated that about 10,000 demonstrators were at the rally. Thousands came into the German financial capital from other parts of Europe.

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Police and Blockupy anti-capitalist protesters face-off near the European Central Bank (ECB) buildingKai Pfaffenbach/Reuters
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Firefighters extinguish police vehicles set on fire by Blockupy protesters near the European Central Bank buildingRalph Orlowski/Reuters
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A policeman stops a protester near the European Central Bank buildingMichael Dalder/Reuters
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A policeman detains one of the anti-capitalist Blockupy protesters in FrankfurtKai Pfaffenbach/Reuters
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Police detain a wounded anti-capitalist protester near the European Central Bank buildingMichael Dalder/Reuters

Hundreds of officers ringed the ECB headquarters ahead of the inauguration ceremony. Protesters are targeting the ECB because of the bank's role in supervising efforts to restrain spending and reduce debt in financially troubled countries such as Greece.

"Our protest is against the ECB, as a member of the troika, that, despite the fact that it is not democratically elected, hinders the work of the Greek government. We want the austerity politics to end," Ulrich Wilken, one of the organisers, said. "We want a loud but peaceful protest," he told Reuters.

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Police remove a road block set up near the ECB building in FrankfurtKai Pfaffenbach/Reuters
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Paving stones are seen on a road during an anti-capitalist protest near the European Central Bank buildingKai Pfaffenbach/Reuters
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A roadblock made of tyres burns outside the EC) building hours before the official openingMichael Dalder/Reuters
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Firefighters extinguish a luxury car that was set on fire by anti-capitalist protesters outside the European Central Bank (ECB) buildingMichael Dalder/Reuters
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Riot police clash with protesters dressed as clowns on the opening day of the European Central BankDaniel Roland/AFP
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Smoke engulfs the city skyline during a Blockupy protest near the European Central Bank building (top R)Reuters

Frankfurt police spokeswoman Claudia Rogalski described the mood of the crowd as aggressive. "We've had stone throwing, burning rubbish bins and seven police cars were damaged, many set on fire," she said.

ECB President Mario Draghi was due to make a speech at the new ECB headquarters at 11am.

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Activists march in a demonstration organised by the Blockupy movement to protest against the policies of the European Central BankThomas Lohnes/Getty Images
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Police detain members of the Blockupy anti-capitalist movement near the European Central Bank (ECB) buildingMichael Dalder/Reuters
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An anti-capitalist protester is detained by police near the European Central Bank (ECB) buildingMichael Dalder/Reuters
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Riot police are seen through the heat haze of a burning barricadeKai Pfaffenbach/Reuters
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A protester lies on the pavement in front of a group of German riot police officers near the European Central Bank buildingKai Pfaffenbach/Reuters
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Anti-capitalist protesters hold a banner reading "Caviar for all" near the European Central Bank buildingKai Pfaffenbach/Reuters
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An anti-capitalist protester dressed as a clown shouts behind policemen near the European Central Bank buildingMichael Dalder/Reuters
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Anti-capitalist protesters scuffle with police before the official opening of the new ECB new headquarters in FrankfurtRalph Orlowski/Reuters
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European Central Bank President Mario Draghi and Vice President Vitor Constancio arrive for the inauguration of the ECB's new headquarters in FrankfurtWolfgang Rattay/Reuters
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German police officers stand outside the conference hall inside the European Central Bank buildingWolfgang Rattay/Reuters
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Protesters walk past a burnt-out car on the opening day of the European Central Bank in FrankfurtOdd Andersen/AFP
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An anarchy sign made of paving stones is seen in FrankfurtSimon Hofmann/Getty Images
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A policeman's riot stick is seen during a demonstration organised by the Blockupy movementSimon Hofmann/Getty Images
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Activists march during an anti-capitalist demonstration in FrankfurtThomas Lohnes/Getty Images
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Anti-capitalist protesters march in Frankfurt on the opening day of the new ECB headquartersThomas Lohnes/Getty Images
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A protester dressed as a clown laughs at a police officer covered in paintThomas Lohnes/Getty Images
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A Blockupy protester dressed as a clown taunt riot police in FrankfurtThomas Lohnes/Getty Images
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Anti-ECB protesters are seen through a shattered bus stop in FrankfurtThomas Lohnes/Getty Images
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Protesters are detained by police in FrankfurtThomas Lohnes/Getty Images
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An injured woman is seen as activists clash with policeThomas Lohnes/Getty Images
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Activists clash with police during a demonstration organised by the Blockupy movement on the opening day of the European Central Bank headquartersThomas Lohnes/Getty Images
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ECB President Mario Draghi prepares to cut the ribbon, flanked by Tarek Al-Wazir and Peter FeldmannWolfgang Rattay/Reuters
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European Central Bank President Mario Draghi cuts the ribbon during the inauguration of the ECB's new 1.3-billion-euro headquarters in FrankfurtWolfgang Rattay/Reuters
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Activists sit on a street in Frankfurt after the ECB officially inaugurated its new headquartersSimon Hofmann/Getty Images
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Riot police begin removing protesters from a street in FrankfurtSimon Hofmann/Getty Images
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Protesters sitting on a street in Frankfurt laugh as police carry one of them awaySimon Hofmann/Getty Images

The ceremony went ahead as planned, with ECB President Mario Draghi saying the new building for the euro bloc's monetary authority was "a symbol of what Europe can achieve together."

Police said 350 people were detained as officers pursued what they said was a minority of violence-minded activists using the protest as cover. The bulk of demonstrators conducted themselves peacefully, marching in groups, drumming and singing ahead of a rally in the city's main square.

Some 10,000 people gathered on Frankfurt's main square, the Roemerberg.

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Thousands of anti-capitalist protesters protest on the Roemerberg, the central square in Frankfurt's old townThomas Lohnes/Getty Images
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Anti-capitalist protesters are seen in the central square in Frankfurt's old town after the inauguration of the European Central Bank (ECB)headquartersKai Pfaffenbach/Reuters
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An activist takes part in a demonstration on Frankfurt's main square, the RoemerbergThomas Lohnes/Getty Images