The German daily Bild said Wednesday in an unpublished report by the Federal Office for the Protection of the Constitution that the leftist Communist Platform, Marxist Forum and pro-Cuba groups, which the report says are "extremist structures," are increasing their influence in The Left Party, Der Spiegel reported.

The Communist Platform, the report says, aims to increase its power in the government by advocating an "overthrow of capitalism," while the Marxist Forum embraces the ideology of the Socialist Unity Party that governed the former East Germany prior to reunification.

Both parties, Der Speigel says, embrace the Geraer Dialogue/Socialist Dialogue movement in The Left Party which the report says is a "receptacle for extremists forces" pushing for "the extra-parliamentary struggle for social change."

The constitutional protection office monitors fringe groups, including terrorist groups and the Scientology organization. A report from 2006 says there are 6,000 left-wing groups in Germany who may use political violence.

The report on extremists goes public Thursday.