This is reported by the radio station France Bleu.
According to the BFMTV channel, on the night of November 19, a teenager died in a knife attack in the commune of Crépal.
"Far-right activists ... It is estimated that between 50 and 100 people... took to the streets of the Monet quarter in the city of Roman-sur-Isère," the radio station said in a statement.
It is noted that out of 20 detainees, three were injured.
The protesters were allegedly demanding justice for the deceased teenager.
In October, French President Emmanuel Macron said there were security problems throughout France.