Updated

The German government says it is investigating the extent of far-right activity in its armed forces after an officer was arrested last week on suspicion of planning an attack.

Prosecutors believe 28-year-old army lieutenant Franco A. had long-standing far-right views and may have been part of a small extremist cell.

A defense ministry spokesman confirmed reports that the suspect, whose full name wasn't released due to German privacy rules, had written a university thesis in 2014 which included "extremist views," but only received a warning.

The spokesman, Boris Nannt, told reporters Wednesday that the decision had been a "mistake."

Defense Minister Ursula von der Leyen on Wednesday visited the barracks in Illkirch, France, where A. had been stationed as part of a Franco-German brigade.