More than 7,400 police will be deployed, aided by drones to give them an overview of the protests and a quicker way to head off potential violence. "Tomorrow, there is a risk," said Interior Minister Christophe Castaner, adding that the goal is to protect demonstrators with "legitimate aspirations" and defend Paris from calls on social media to make it "the capital of rioting."
Authorities fear that 1,000 to 2,000 "radical activists" could descend on the May Day marches, bolstered by people from outside France, he told a news conference. He said other cities around France were also on alert.
French police have banned demonstrations on the Champs-Elysees Avenue, around the presidential palace in Paris and near Notre Dame Cathedral, which was gutted by devastating fire on April 15. Among a raft of other security measures, French police ordered over 580 shops, restaurants and cafes on the Paris protest route to close and plan to search demonstrators' bags and carry out identity checks at departure points into Paris, including train and bus stations.
The main union protest on Wednesday runs from Montparnasse train station in Paris to the Place d'Italie station in southern Paris. Castaner also told reporters that he had banned the arrival of several "foreigners identified as susceptible of coming to destroy."
Paris has been scarred by looting, arson and violence during the past few months of yellow vest protests over economic grievances, and French authorities are haunted by the serious violence that has broken out at May Day demonstrations in the past two years.
Authorities are particularly wary of the black-clad, masked and hooded extremists who have joined recent protests with the express goal of attacking police and damaging property. They often target symbols of capitalism or globalization, and turned out in the hundreds at last year's May Day protest.
French President Emmanuel Macron last week tried to address the complaints of the yellow vest movement by announcing tax cuts for middle-class workers and an increase in pensions. But many yellow vests consider the government's plans insufficient, and want to keep alive the movement that started in November to oppose a fuel tax and quickly expanded into broad public rejections of Macron's economic policies.
The movement was named after the fluorescent jackets that French motorists are required to keep in their cars.
Elaine Ganley contributed from Paris.