(CNN) Rail workers across France have gone on strike for the first day of a three-month rolling walkout, the latest and potentially biggest battle over labor laws in the country since President Emmanuel Macron took office last May promising to transform the jobs market.

Train services have been severely disrupted, with around 87% of high-speed trains and 80% of regional services canceled Tuesday, according to SNCF, France's state-owned rail company.

Eurostar services were also affected, with one in four services from Paris canceled. High-speed Thalys trains towards Belgium and the Netherlands were operating almost as normal, but there were no services towards Switzerland, Spain or Italy.

Tuesday's walkout -- dubbed "Black Tuesday" by the French media -- comes less than two weeks after a nationwide strike across the public and transport sectors as workers protested the government's proposed labor overhauls, including the plans to open the SNCF to competition.

Unions have called for the "strongest possible" strike to protest proposed reforms that they believe would lead to the privatization of the railways, and to call for higher wages and an end to precarious jobs. The government said there were no plans to privatize SNCF, which is 45 billion euros ($56 billion) in debt, according to Reuters

"We're striking for several reasons, but at the top of the list is the government wanting to open up the service to competition," the spokesman for rail union Sud Rail, Eric Santinelli, told CNN. "They don't want to do it in a progressive manner, they want to do it in an accelerated manner."

Both sides have made it clear that they will not concede, and each sees the strikes as a test of their resolve and credibility. The government believes it is acting with a mandate for change, but the unions have always succeeded in making the government back down.

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The walkout, which began at 7 p.m. local time Monday and will end at 8 a.m. Thursday, is the first of 18 two-day walkouts planned before the end of June. The next is scheduled for April 8-9.

In an IFOP poll published Sunday in the Journal du Dimanche newspaper , 53% of the nearly 1,000 people surveyed said the strike was unjustified.

Other sectors could join the strike as it continues in protest at broader changes to labor laws proposed by Macron.

Unions fear that if Macron triumphs in the rail dispute, he could soon push through controversial reforms in areas such as education and pensions.

Air France workers also walked out Tuesday in a separate and continuing dispute over pay, leading to the cancellation of around 25% of flights. Three further strike days are planned in the next ten days.

A passenger crosses the tracks at Gare de Lyon train station in Paris on Tuesday.

Poll: French divided over reforms

After winning 66% of the vote in a run-off with far-right candidate Marine Le Pen in last year's presidential election, Macron claimed a mandate to overhaul France's labor laws, the raison d'être of his candidacy. His pledge echoed the promises of several previous French presidents, none of whom were able to implement the changes due to strong union opposition.

In a series of five executive orders last August, Macron laid out his goals: to give companies more flexibility in hiring and firing workers, more power to negotiate working conditions directly with employees, and less financial risk in cases of wrongful dismissals.

Just over half (51%) of those surveyed in Sunday's IFOP poll said they support the reforms.

Macron's plan to turn the state-owned SNCF into a profit-making business has raised particular concerns among its employees, who fear they could lose job-for-life guarantees, annual pay rises and the right to early retirement. Union bosses have also expressed concern that increasing the competitiveness of the railways could mean increased ticket prices for travelers.

'This type of competition is savage'

France's transport minister Elisabeth Borne said there were no plans to privatize SNCF and suggested that opening up the country's high-speed trains to competition would mean "more trains, new services, cheaper tickets."

"This reform is necessary for travelers, necessary for the SNCF, necessary for the railway workers," she told CNN's affiliate BFM TV on Tuesday.

Borne also said she was looking for dialogue with the unions, a claim that Santinelli, the rail union spokesman, disputed.

"The reality is she wants to create a law which opens us up to competition and it is out of the question that we will write a law that includes that," he told CNN.

"Our vision is of a railway system offering a public service. She's suggesting private companies that will use the SNCF personnel; this type of competition is savage and it's unacceptable."

A man wearing a jacket reading "angry railway worker on strike" at a Marseille train station on Tuesday.

The French government has been trying to push through changes to labor laws for decades, with one of the strongest drives coming in 1995 . Then-Prime Minister Alain Juppe had proposed restructuring SNCF and raising the retirement age for train drivers.

He was forced to concede after the country's unions sent thousands to the streets in demonstrations and, in the minds of many, turned the protest movement into a battle for the soul of the country, winning widespread public support.

"Either the government starts really negotiating or we'll just keep on going," he said.