Marion, 29, said a man had tried to film her in the Paris Métro.
"He was -sitting opposite me and I saw him -trying to film under my skirt with his -mobile phone. I raised my voice and told him to stop... He did... muttering and staying calmly in his seat."
According to a survey, half of all women in France wear trousers on public transport to avoid harassment.
Some say they have taken to wearing shorts under their skirts to defend themselves against 'upskirting'.
One woman, Adèle, told Le Parisien that she had grabbed and broken the phone of a man who filmed her on the Métro.
One 17-year-old said she had felt violated -after being filmed on an escalator in a shopping centre.
'Upskirting' is already illegal in Belgium, but police say few women report it to the police.
Olivier Slosse, a Brussels police spokesman, urged more women to report 'upskirting' or voyeurism.
"We only get about 20 complaints a year for this kind of voyeurism," he said.
"It's important for the victims to come forward because they are the victims of an illegal act and it's important for us because these crimes are under-reported and it helps draw our attention to them."
A proposed law to ban 'upskirting' was blocked in the UK by Sir Christopher Chope, a senior Tory MP.
Prime Minister Theresa May has since revealed plans to push the law through.