Controversial German aristocrat Prince Ernst August of Hanover is under investigation for allegedly making a Hitler salute, just days after he was heavily fined for attacking a man, a report said on Wednesday. Ernst August, the husband of Princess Caroline of Monaco, is said to have insulted a member of staff and made the gesture with his right arm during a recent security check at Hanover airport, investigator Thomas Klinge from the Hanover prosecutor's office told Bild mass-circulation daily. The prince is accused of "using symbols of organizations banned by the constitution." All symbols of the Nazi era are banned in Germany. Ernst August was fined €445,000 ($590,000) by a court Thursday for attacking the German owner of a hotel and disco on the Kenyan island of Lamu in January 2000. His lawyer told the court he had been under the influence of alcohol at the time of the attack, which left the man needing hospital treatment.