The raids took place in Berlin, Brandenburg, Lower Saxony, Saxony-Anhalt and Baden-Württemberg and were the result of a joint federal and state operation involving some 300 officers.
The investigation is thought to centre on nine suspected members of the 'Militante Gruppe' (MG) leftist extremist organisation, which carried out multiple arson attacks on state agencies between 2001 and 2009.
One of the current suspects was sentenced to three years in prison for an attempted attack on German army vehicles in 2009.
Nine homes of suspected members of the radical 'Revolutionäre Aktionszelle' (RAZ) organisation, which emerged as a follow-up to the 'Militante Gruppe' in 2009, were among the properties searched, the online edition of Der Spiegel reported.
That group has claimed responsibility for multiple attacks, including the planting of bombs outside a district court and job centre in the Berlin district of Wedding, and a state property in Charlottenburg between 2009 and 2010.
The RAZ also claimed responsibility for sending a bullet to Interior Minister Hans-Peter Friedrich, among others, in March 2011. The package was accompanied by a note identifying the group and promising the next delivery would be "by express."
The group's activities have been described as inspired by a "battle of classes," and driven by the principles of anti-imperialism and social revolution.