What we know about the violent protesters at the G-20 summit

Police described figures in masks and hoods causing chaos in Hamburg.

ByJULIA JACOBO
July 06, 2017, 5:55 PM

— -- Hamburg police described the violent protesters clashing with police as members of a black bloc, wearing masks and hoods as they ignited fires on the street and threw objects at officers on the scene ahead of the G-20 summit in Germany.

The violence was driven by the same brand of black-hooded youths that have stirred up trouble at past summits.

PHOTO: German riot policemen catches protester during the demonstrations during the G-20 summit in Hamburg, Germany, July 6, 2017.
German riot policemen catches protester during the demonstrations during the G-20 summit in Hamburg, Germany, July 6, 2017.
Kai Pfaffenbach/Reuters

The term "black bloc" is used to describe a group of people wearing black clothing such as hoodies, masks and scarves to conceal their identities. A black bloc is typically considered to be an anarchist group.

In Hamburg on Thursday, members of the black bloc held a large banner that read, "Welcome to Hell," which was the name of today's protest.

PHOTO: Police block demonstrators during the "Welcome to Hell" rally against the G-20 summit in Hamburg, northern Germany on July 6, 2017.
Police block demonstrators during the "Welcome to Hell" rally against the G-20 summit in Hamburg, northern Germany on July 6, 2017.
John MacDougall/AFP/Getty Images

Officers used water cannons and pepper spray to disperse the violent crowd, police said. Dozens of police officers were injured, including one who suffered an eye wound after a firecracker exploded in their face.

PHOTO: A man makes a gesture at police as he is drenched in water from water cannons during the "Welcome to Hell" protest march on July 6, 2017 in Hamburg, Germany.
A man makes a gesture at police as he is drenched in water from water cannons during the "Welcome to Hell" protest march on July 6, 2017 in Hamburg, Germany.
Alexander Koerner/Getty Images

Out of 8,000 people in the crowd, police estimated about 1,000 to be associated with the black bloc, they said.

In 2017, black bloc protesters have appeared all over the world. On Wednesday, in Rio de Janeiro, Brazil, masked demonstrators held shields to protest Brazilian President Michel Temer's proposed reform for the country's social security system.

PHOTO: Demonstrators from a group called Black Bloc hold shields at a protest against President Michel Temer's proposal reform of Brazil's social security system during a general strike in Rio de Janeiro, Brazil, June 30, 2017.
Demonstrators from a group called Black Bloc hold shields at a protest against President Michel Temer's proposal reform of Brazil's social security system during a general strike in Rio de Janeiro, Brazil, June 30, 2017.
Pilar Olivares/Reuters

On May 1, black bloc protesters participated in May Day demonstrations in Paris.

PHOTO: Black Bloc protesters push a shopping trolley with a cardboard dragon face towards police force during the May Day marches in Paris, May, 1, 2017.
Black Bloc protesters push a shopping trolley with a cardboard dragon face towards police force during the May Day marches in Paris, May, 1, 2017.
Salvador Banyo/NurPhoto via Getty Images

Black bloc demonstrators also participated in May Day protests in Berlin, where more than 5,000 police were on the scene to maintain order, since demonstrations in past years had led to street battles between demonstrators and police.

PHOTO: Demonstrators clash with riot police during a May Day march by left-wing protesters in Kreuzberg, May 1, 2009 in Berlin.
Demonstrators clash with riot police during a May Day march by left-wing protesters in Kreuzberg, May 1, 2009 in Berlin. Over 5,000 police officers are in Berlin to maintain order during the myriad of May 1, Workers Day, demonstrations that in years past have traditionally led to street battles between drunken demonstrators and police.
Sean Gallup/Getty Images

After chaos broke out in Hamburg on Thursday, police moved to arrest violent protesters in the crowd.

More than 100,000 protesters are expected in Hamburg for the summit, which include about 8,000 people considered part of Europe's violent left-wing scene, The Associated Press reported. Some 20,000 police officers have been activated to keep the demonstrations under control amid high tensions.

ABC News' Kirit Radia and Sarah Hucal contributed to this report.

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