Story highlights Three police officers hospitalized after violence in anti-capitalist march in London

The march, organized by hacker collective Anonymous, led to 50 arrests, police said

Police: Police car burned, six police horses injured and three arrested on weapons charges

London (CNN) A Million Mask March through central London organized by hacker collective Anonymous erupted in violent scenes Thursday night, with three police officers taken to the hospital, a police car set ablaze and 50 people arrested, police said.

In a statement, Metropolitan Police commander BJ Harrington condemned the violence as "completely unacceptable" and praised his officers for their restraint "in the face of hostile provocation." Six police horses were also injured.

About 2,000 police officers were called into action, with mounted officers forming a barrier against a densely packed crowd on The Mall.

The march was held on Guy Fawkes Night, an annual commemoration in the UK of a failed plot to kill King James I in 1605. It's usually celebrated with bonfires and fireworks. Many of the protesters wore stylized Guy Fawkes masks adopted by the Anonymous movement and lit fireworks as the march passed by the British capital's landmarks.

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