St. Pauli's iconic symbol has been added to the UK anti-terrorism watch list. Christian Charisius/picture alliance via Getty Images

The badge of German second tier side St. Pauli has been added to a document of symbols to be wary of which the UK counterterrorism police has distributed to various public sector workers across the country.

Among the other symbols on the list, which the UK government believe represent a possible terror threat, are swastikas and symbols representing Jihadi groups.

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St. Pauli, who are based in the German city of Hamburg, are famous for their left-wing political leanings. Their badge, a skull and crossbones, appeared under the heading "Left Wing Signs & Symbols Aid" -- alongside "Stand Up To Racism," "Anti-Fascism Network" and "Unite Against Fascism."

The document is used as guide for "Prevent," an anti-radicalisation scheme aimed at catching those at risk of committing acts of terror, and was presented at public sector briefings last year and has since been uncovered by The Guardian.

St. Pauli have been known to hold up banners welcoming refugees to Germany and showed their support for the Kurdish people following the conflict in the Middle East. They have also been involved with clashes against neo-Nazis at various away matches.

The club have been taking a stand against racism and homophobia for many years and on one of the stands a "No Football For Facists" banner is displayed at every match. Their traditional skull and crossbones logo is the club's unique marketing tool and has, in parts, been detached from the footballing department.

It is worn by left-wing people across the world, with one of their fan clubs, the East River Pirates, based in New York. St. Pauli have toured with great success across the United States in two consecutive years. Their latest trip in May 2019 took them to New York and Buffalo.

James Lawrence, a defender at the German club, expressed his support for St. Pauli in an Instagram post, which read: "Proud of the values we have. Proud to play for St. Pauli. Anti-Fascist, Anti-Racist, Anti-Sexist and Anti-Homophobic. What's not to like!"

St. Pauli responded with a tweet, which said: "Well said, James Lawrence! Nothing for us to add really, apart from lots of love for James perhaps."

Information from ESPN's Germany correspondent Stephan Uersfeld was used in this report