A 'Yellow Vest' rally saw violent clashes between protesters and riot police in Montpellier on Saturday.
At least 21 people were arrested and three police suffered injuries, according to the Herault police prefecture.
The clashes were centred around Place de la Comedie, where some 1,000 people refused to leave for over four hours.
The police responded with tear gas and water cannon.
Several shops were targeted by vandals, while police reported stone-throwing from hardcore 'ultras'.
The movement, whose members wear yellow high-visibility jackets, oppose the status quo in France and see French President Emmanuel Macron as propping up the elite at the expense of ordinary citizens.