Prosecutors are investigating a leading member of the nationalist Alternative for Germany party following reports he sold Nazi-era memorabilia.

Rudolf Mueller, the party's top candidate for elections in the western state of Saarland next year, allegedly sold medals and currency used in Nazi internment camps at his antiques store.

The claims were first reported by weekly Stern and public broadcaster ARD.

Saarbruecken prosecutors said Thursday that they are probing whether Mueller broke the law banning the use of symbols deemed to be in breach of Germany's constitution. Such symbols include the Nazi swastika that was often found on German World War II medals.

Mueller says he doesn't believe he broke the law.

Alternative for Germany has been dogged by allegations of anti-Semitism and far-right links among its members and supporters.