German police say they have discovered evidence of Reich Citizens' Movement members in their own ranks, following the fatal shooting of a German police officer by a member of the Reichsbürger group in Bavaria.

German newspaper Sueddeutsche Zeitung reported Sunday that the number of internal disciplinary matters related to the Reich Citizens' Movement across German police forces have increased markedly recently. A total of 15 cases are now being investigated across the country, Sueddeutsche said, after a survey of Germany's state interior ministries. Bavaria is the federal state with the most cases, the newspaper said. A 26-year-old officer was suspended there last week. He was the sixth suspected member of the Reich Citizens' Movement in the state.

Members of the movement do not recognize the modern German state and its laws, but believe the former German Reich still exists. Germany's far-right National Democratic Party (NPD) should be banned because it espouses Nazi ideology and incites hatred against migrants, two politicians argued before the country's highest court on Thursday.

The Constitutional Court is hearing a landmark request from Germany's 16 federal states - represented by the upper house of parliament, the Bundesrat - to ban the ultranationalist party, which has been known to glorify Third Reich leaders and trivialize Nazi crimes. On the third and final day of the hearing, Joachim Hermann, the interior minister of Bavaria, accused the party of "spiritual arson" - a term used in Germany to denounce incitement - that could lead to further violence against refugees and their accommodation. In order to ban a political party, the states must prove the NPD's ideology is "combative and aggressive" and poses an active threat to the democratic order. A previous attempt to ban the party failed in 2003 because the presence of undercover informants from the domestic intelligence agency in its upper echelons was seen as weakening the evidence.