Rome - The photo of a young Italian woman kissing a police officer's helmet visor during a protest has gone viral, with a police union threatening to sue her for "sexual violence". The 20-year-old student, Nina De Chiffre, was snapped by a photographer working for AFP as she went to kiss the policeman, Salvatore Piccione, at a protest against a new high-speed rail line in the Alps. Her act was interpreted by many as a loving gesture and proved a hit on social media, although the photographer Marco Bertorello and De Chiffre herself pointed out that it was intended as an act of mockery. The 16 November demonstration had brought thousands of protesters to the picturesque Val di Susa where the contested line is being built between France and Italy. Franco Maccari, the head of the Coisp police union, earlier this month vowed to sue the protester for "sexual violence and insulting a public official". Contacted by AFP, prosecutors said they had not received a lawsuit but said one could still be submitted for 90 days after the protest.