Greek authorities have brought indecency charges against a US national who allegedly pranced naked at a prominent Athens war memorial following an anti-austerity protest outside parliament.

The 56-year-old man, who was not identified, was arrested late on Tuesday in the aftermath of a 50,000-strong rally during a visit by German Chancellor Angela Merkel.

A video posted online showed a stark naked man in his fifties talking to presidential guards at the Unknown Soldier’s Tomb in front of parliament, which had been fenced off for the protest. Police officers first remonstrated with him and, when he carried out a little jig, cheered on by a few remaining protesters, led him away.