The organisation represents the far left of the German political spectrum and counts among its number some 90 political organisations.
These include Die Linke, a party which stands to the left of the Social Democratic Party (SPD) and which grew out of the communist party of east Germany.
Also prominent are anti-capitalist activist group Attac, some trade unions and anti-fascist groups, reports Der Spiegel.
Blockupy also has an international representation, with organisations from France, Spain, Italy and Denmark involved.
What are its goals?
Blockupy states its aim as “resistance within the heart of the European crisis regime.”
By “crisis regime” it refers to the so-called Troika of the European Central Bank, The European Commission and the International Monetary Fund which have been negotiating debt deals with Greece since 2012.
“The aim of the “institutions” [the Troika] and their clients is to subjugate all of Europe to a debt that can never be repaid,” reads a statement on their website.
Was violence expected?
The police announced on Tuesday that there was a “high probability” that there would be violence.
Earlier in March anti-fascist groups attacked the police and marchers at a protest by anti-islamic organisation Pegida in central Frankfurt, seriously injuring at least one demonstrator.
In May 2012 protesters at a left-wing rally seriously injured a police officer, when a demonstration spiralled out of control and ended up causing nearly €1 million's worth of damage in Frankfurt city centre.
What do Blockupy say about the violence?
Ulrich Wilken, a Die Linke politician, who organised the demonstration, said at a press conference on Wednesday: "I want to say that this morning did not go as we had wished. This is not what we had planned... I understand the great outrage... but this is not how German demonstration culture should be."
In an earlier conversation with Berlin-Brandenburg Rundfunk, he explained the violence by saying that people who are affected by the Troika's policies “are very angry.”
On their official Twitter feed @blockupy, the organisation has so far posted pictures of the peaceful protests which are taking place. It has largely ignored the violence.
The Twitter feed also complains about police tactics, saying that police have “kettled” protesters. It encourages others to come and show their support.
Kettling is a police tactic of surrounding protesters, sometimes for hours at a time, blocking their ability to leave the area.