Authorities in Berlin are investigating an 18-year-old student on suspicion of defaming Chancellor Friedrich Merz during a student protest against the country's recently introduced military service.

The suspect reportedly touted a poster with the slogan "Merz leck Eier" (Lick my balls Merz) during the demonstration on Thursday afternoon.

Police officers confiscated the poster and launched an investigation on suspicion of slander and libel against persons in political life, a police spokesman said on Friday.

The newspaper Junge Welt reported on the incident and showed a photo of the man with the poster on its X channel.

According to Germany's Criminal Code, defamation statutes apply when someone knowingly asserts or disseminates untrue statements about another person that are likely to disparage or demean them in public opinion.

Following a recent visit by Merz to the southern city of Heilbronn, police investigated several people for possible insults expressed in a Facebook post.

This terms concerned included "Pinocchio" or "Lackaffe" (which roughly translates as "fop" or "dandy") that users posted under a police post about Merz's visit.

The police are obliged to look into the matter, a spokesman said: "If we have an initial suspicion of a criminal offence, then we must pursue it."