Railway workers, teachers and emergency room medics launched one of the biggest public sector strikes in France for decades on Thursday, determined to force President Emmanuel Macron to abandon plans to overhaul France’s generous pension system.

Transport networks in Paris and beyond ground to a near halt as unions dug in for a protest that threatens to paralyse France for days and poses the severest challenge to Macron’s reform agenda since the “yellow vest” protests erupted.

Riot police in Nantes, western France, fired tear gas at masked protesters who hurled projectiles at them. In Lyon and Marseille, thousands more protesters carried banners that read “Macron get lost” and “Don’t touch our pensions”.

“What we’ve got to do is shut the economy down,” Christian Grolier, a senior official from the hard-Left Force Ouvriere union, said.

Commuters in Paris dusted off bicycles, turned to carpooling apps or worked from home to avoid the crush on the limited train and metro services that operated in the morning rush hour.

Airport workers, truck drivers and police are joining the strike at a time of widespread discontent towards Macron’s drive to make France’s economy more competitive and cut public spending. French law requires minimum public services are maintained during a strike.

Macron wants to simplify France’s unwieldy pension system, which comprises more than 40 different plans, many with different retirement ages and benefits. Rail workers, mariners and Paris Opera House ballet dancers can retire up to a decade earlier than the average worker.

Macron says the system is unfair and too costly. He wants a single, points-based system under which for each euro contributed, every pensioner has equal rights.

For the former investment banker, the showdown with strikers will set the tone for the second half of his mandate.

Nor is it without risk for the hard-Left unions whose membership and influence have diminished in recent years. They face a delicate balancing act of needing to pressure the executive while not creating a public backlash.

“For 30 years successive governments have tried to bring reform and fail because the unions cripple the country,” said 56-year-old cafe owner Isabelle Guibal.