German authorities arrested a man they say has ties to a neo-Nazi cell calling itself the National Socialist Underground, federal prosecutors said in a statement. Holger G., 37, was arrested on suspicion of being a member of the group since the late 1990s.

Interior Minister Hans-Peter Friedrich  warned Sunday of a new type of far-right terrorism. “We appear to be dealing with a new form of right-wing terrorism,” he said, as details of a grotesque film left by members of a neo-Nazi cell in eastern Germany emerged, in which they claimed to have murdered nine immigrants between 2000 and 2006. The murders were committed in several German cities.

Eight ethnic Turks, an ethnic Greek and a policewoman were murdered. All victims managed small businesses or fast-food stands, across Germany, which led to the killings being dubbed the doner murders. The group came to light only this week after one alleged member surrendered and two others killed themselves. The suspected accomplice, known as Beate Z., surrendered on Tuesday after allegedly blowing up the flat she had rented in the eastern town of Zwickau, while police identified the two men found dead in the caravan as Uwe B. and Uwe M.

The two dead men left behind four DVDs in the rubble of their Zwickau apartment in which they proclaimed their anti-immigrant motives and threatened further attacks.

Germany is home to some 3 million people of Turkish origin. Protesters, many with Turkish roots, gathered at the Brandenburg Gate in Berlin on Sunday night, to protest against neo-Nazis.

Chancellor Angela Merkel called investigators' initial findings alarming, and said they revealed structures which authorities had been unaware of.