The suspect is alleged to have sold illegal weapons online and called for "defense" against migrants.
He may also be behind right-wing extremist websites and another online weapons shop.
The suspected owner of an online shop selling illegal weapons to Germans has been arrested in Hungary, state prosecutors in Berlin.
The 35-year-old right-wing extremist Mario R. is alleged to be behind the internet website "Migrantenschreck," which roughly translates as "Migrant fright."
The site sold illegal weapons to Germans to defend against migrants and left-wing groups.
Hungarian police arrested Mario R. after German authorities issued an arrest warrant.
A joint German and Hungarian team were reportedly investigating his house and computers.