The most serious nationwide strike to hit France in years caused new misery for weekend travellers on Saturday, with unions dismissing proposals by the government and warning walkouts would last well into next week.

The challenge thrown down to President Emmanuel Macron over his plans for radical pension reform has prompted hundreds of thousands to take to the streets and brought key transport services to a standstill.

Hundreds of thousands have taken to the streets in France over Macron's plans for radical pension reforms
Hundreds of thousands have taken to the streets in France over Macron's plans for radical pension reforms AFP / Zakaria ABDELKAFI

The strikes, which began on Thursday over the plans for a single points-based pension scheme, recall the winter of 1995, when three weeks of huge stoppages forced a social policy U-turn by the then-government.

Unions have vowed a second series of mass demonstrations nationwide on Tuesday after Thursday's big rallies and there is expected to be little easing of the transport freeze over the coming days.

Prime Minister Edouard Philippe said the government was prepared to ease in the plan more gradually
Prime Minister Edouard Philippe said the government was prepared to ease in the plan more gradually AFP / Bertrand GUAY

The strikes could prove to be the biggest domestic challenge yet for Macron, who came to power in 2017 on the back of promises to radically reform France and has sought a prominent place on the international stage as Europe's number one statesman.

Macron was widely believed to have ridden out the challenge posed by the "yellow vests" whose weekly Saturday protests against inequality in France had shaken the government over the last year.

But the yellow vests have also sought to use the momentum of the strike movement and held a fresh protest in Paris on Saturday and others in several cities across France.

The walkout is the latest test of Macron's mettle
The walkout is the latest test of Macron's mettle AFP / Zakaria ABDELKAFI

Police and local authorities estimated the turn-out across France at 23,500 -- of whom 1,600 marched in Paris. The organisers of such marches routinely dismiss these official counts as gross underestimates.

Paris's Gare de Lyon station was almost completely empty
Paris's Gare de Lyon station was almost completely empty AFPTV / Mathieu CHAMPEAU

Prime Minister Edouard Philippe has insisted that the government will not abandon the plan, though he added it was prepared to bring it in gradually.

He did not want "confrontation", he added.

Unions say Macron's proposal for a single pension system would force millions of people to work well beyond the official retirement age
Unions say Macron's proposal for a single pension system would force millions of people to work well beyond the official retirement age AFP / Zakaria ABDELKAFI

But the leader of the hardline CGT union, Philippe Martinez, said of the prime minister Saturday: "He is doing everything to ensure that the strikes last."

In a joint statement, the three main rail unions called for the strike to be stepped up on Monday.

While most of the rallies Thursday were peaceful, police fired tear gas to disperse dozens of protesters
While most of the rallies Thursday were peaceful, police fired tear gas to disperse dozens of protesters AFP / BULENT KILIC

The SNCF rail operator has warned that disruption at the weekend will be at the same level as the last two days, with just 10-15 percent of high-speed and regional trains running.

Transilien, the operator of the Paris region rail network warned of severe shortages Monday. To avoid what could be "dangerous" levels of overcrowding, it recommended using other means of transport such as car-sharing.

The Paris metro will also remain severely disrupted with only the network's two driverless lines working normally.

The international Eurostar and Thalys rail services have been hit by cancellations. Air travel however was returning closer to normal Saturday, as the civil aviation authorities dropped air traffic restrictions.

Unions say Macron's proposal for a single-pension system would force millions of people in both the public and private sectors to work well beyond the official retirement age of 62.

At least 800,000 took part in rallies around the country on Thursday, according to the interior ministry -- one of the biggest demonstrations of union strength in nearly a decade.

A crucial week now lies ahead: commuters will struggle to get to work on Monday and more giant nationwide protests are planned for Tuesday.

Then on Wednesday, Philippe is due to unveil full details of the reform which could spark more union anger.

Tourists in Paris also faced some disappointments: the world-famous Louvre Museum said some rooms would be closed due to the strikes, while the landmark exhibition of painter El Greco at the Grand Palais was closed.

The Paris Opera and several theatres in the capital have cancelled performances over the last few days due to the strike.

And businesses feared that the lack of transport would hit shopping on a key weekend in the run-up to Christmas.

In the southeastern city of Lyon, where hotels are usually full to bursting at this time of year for a light festival, hoteliers complained of a lack of custom as travellers put off stays.

"We are down 10 or 20 percent in reservations but for some hotels it is 30 percent," said Lyon hotelier Laurent Duc, head of a national hotel union.