Citing a police source, French news channel BFM TV said the three suspects have been detained in the 10th district of Paris. There, police found in their bags materials that could be used as projectiles, including hammers and screwdrivers in addition to incendiary products, namely three gas cylinders and two cans of gasoline.

They also found a map detailing the route of the main unions' protest which is planned from Montparnasse train station to Place d'Italie metro station in southern Paris, about 2 km apart.

As a heady mix of labor unionists, "yellow vest" demonstrators and other radical activists was expected to hit the streets on May 1, the French government took a "zero-tolerance" approach against violence.

With orders from French President Emmanuel Macron to take an "extremely firm stance" against any kind of violence, more than 7,400 policemen were deployed across Paris, with identity checks and bag searches being reinforced, especially in sensitive sites including train stations.

Fearing violence and destruction of public property, authorities have banned protests and barricaded the neighborhood near the Elysee Palace, the National Assembly and Notre Dame Cathedral.

They also called on shops, restaurants and cafes, located on the demonstration's path, to close by Wednesday afternoon, erect barricades and board up windows for fear of looting.