French teachers walked off the job for the second time in a week Tuesday and demonstrators hit the streets again on the sixth day of a strike over pension reforms that shows no sign of abating.

The strikes have hit Paris the most, with around 35 percent of teachers in the capital walking out, compared to around 12.5 percent nationwide, according to Education Minister Jean-Michel Blanquer.

Meanwhile, public transport in the city remained at a near standstill, with only two of 16 metro lines running as normal, nine completely closed and suburban train services also heavily disrupted.

The work stoppages, which have also ground inter-city trains to a halt and forced the cancellation of dozens of flights, mark the biggest show of union force since President Emmanuel Macron came to power in 2017 vowing to cut public spending and make the economy more competitive.

The head of the Paris commuter rail service, Alain Krakovitch warned Tuesday that he expected the chaos to continue "until the end of the week" but some labour leaders have vowed to fight through until Christmas.

"Pensions are the glue of all discontent," the leader of the hardline CGT union Philippe Martinez told France 2 television.

The strikes have hit Paris the most
The strikes have hit Paris the most AFP / Aurore MESENGE

The unions are hoping to bring hundreds of thousands of people onto the streets again Tuesday to protest over Macron's plans to replace France's 42 separate pension plans with a single points-based system that would require the French to work longer.

More than 800,000 people marched in towns and cities across the country on the first day of the industrial action on December 5.

Beyond the pension reform, many accused former investment banker Macron of trying to roll back France's costly but highly cherished public services.

The government has insisted that the new pension plan, which would do away with the more beneficial schemes covering a host of jobs, from train drivers to ballet dancers, will be fairer for all and more sustainable.

On Wednesday, Prime Minister Edouard Philippe will lift the lid on the details of the overhaul in a highly anticipated speech expected to include several concessions aimed at getting the changes through.

The unions have so far sounded an uncompromising note, insisting that they will not call off the strike unless the pension plan is scrapped outright.