Police detained 22 people on Monday morning after members of an unknown anarchist group broke into the offices of the Hellenic-American Union at around 8 a.m. and held a banner outside the offices reading "Solidarity against slavery."

A group calling itself "The Solidarity Convention for political detainees, prisoners and persecuted fighters" claimed responsibility for the act with a statement posted on the 'net later in the day.

It said the act had been "in solidarity with the fight of detainees protesting slavery in the jails of the USA."