French civil servants angered by Emmanuel Macron's plans to freeze their pay and eliminate 120,000 public jobs go on strike Tuesday, amplifying a revolt over the president's cost-cutting, pro-business agenda.

Nine unions representing 5.4 million public workers have called for a day of nationwide strikes and demonstrations to show their "profound disagreement" with Macron's bid to transform the gargantuan public service.

The protests are the fourth in a series of demonstrations aimed at forcing the 39-year-old president to row back on his reforms. 

"The government does not seem to have taken the full measure of the deep malaise among civil servants," Laurent Berger, head of the CFDT, France's second-biggest union, told Les Echos business daily.

"They are suffering from being seen merely as a budgetary constraint and not as beneficial," he said.

For the first time since 2009, hospital unions have called on medical staff to walk off the job.

Schools are also set to be affected and trains and flights are expected to be delayed. 

Thirty percent of flights in and out of Paris and other major cities have been cancelled.

This is the first time in a decade that all nine public-sector unions have issued a joint strike call.

It comes as Macron -- who has been painted as a "president of the rich" by leftist critics -- continues to take heat for a string of derogatory comments about disgruntled workers.

But Berger and other labour leaders have been divided over how to respond to Macron's far-reaching shake-up of France's labour code.

The hardline CGT union and the hard-left France Unbowed party organised three demonstrations last month over the changes, which make it easier for employers to lay off staff and do deals with workers at the company level, instead of across an industry or sector.

But the protests failed to mobilise the kind of numbers triggered by workplace reforms in 2016, with the CFDT and another large union showing a willingness to compromise.

- 'Facing down the street' -

The CGT and veteran leftist France Unbowed leader Jean-Luc Melenchon are hoping Tuesday's strikes will inject new momentum into their revolt and spur other disgruntled groups to join the fray.

Pensioners and truck drivers are among those who have also demonstrated in the past month, and regional governments are also up in arms at having their funding from Paris cut by 450 million euros ($529 million).

Frederic Dabi of the Ifop polling agency said civil servants saw themselves as sacrificial lambs. 

After giving Macron their backing in the presidential election "they feel they are being made to pay for the government's policies", Dabi told AFP.

Topping their grievances are his plans to freeze their pay, increase their taxes and cut nearly 1,600 civil service jobs in 2018 -- the first swing of the axe in his plan to cut 120,000 public posts by 2022.

But unless other workers down tools, or young people angered by cuts to student housing subsidies take to the streets, Macron will continue to have free rein to implement his agenda, Dabi said.

In a sign that he has the upper hand for now, his poll numbers have recovered slightly after a dramatic slide this summer to around 30 percent.

"What is positive for Emmanuel Macron is that he is seen as facing down the street and implementing his programme," Dabi said.