(CNN)Social media rumors of child abductions by members of the Roma ethnic minority have sparked a wave of violence in France, although authorities have dismissed the claims as baseless.
French police called for calm Monday and said crowds had been attacking people they believed were responsible for the rumored abductions.
In a tweet, police said rumors of a white van driving around the Paris suburbs of Nanterre and Colombes attempting to snatch young women had resulted in the false accusation and "lynching" of two people.
"Do not share this false information," the police tweet continued.
The pair were left with minor injuries after an attack involving around 20 people on March 16, the AFP news agency reported.
Police said the rumors were "completely unfounded" and "no kidnapping has been confirmed" in another tweet Tuesday.
The rumors were focused on people from the Roma ethnic minority, and police arrested 20 people after a number of attacks on the community, a police source told AFP.
In a statement Tuesday, Roma advocacy group La Voix des Rroms said the racist stereotype of a Roma child-thief has been around in France since the Middle Ages.
The group likened anti-Roma aggression to the massacre of the Rohingya in Myanmar, and called on people to form citizen protection groups to guard those whose lives are in danger.
CNN has contacted the group for further comment.
More violence took place on Monday in Bobigny and Clichy-sous-Bois, disadvantaged suburbs northeast of Paris, the source told AFP. There were no reports of injuries in that unrest.
The agency said the rumors appeared to originate from Facebook and Snapchat.
The attacks are "unacceptable," AFP reported government spokesman Benjamin Griveaux as saying. The incidents provided further evidence of "the absolute need to fight 'fake news,'" he added.
"Spreading such rumors in a highly organized and viral way on social media results in violence (and) the stigmatization of a community," he said.