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

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

The strikes, which began on Thursday over the plans for a single points-based pension scheme, have recalled 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 big rallies on Thursday and there is expected to be little easing of the transport freezes over the coming days.

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 utilise the momentum of the strike movement and held a new protest in Paris on Saturday, although there was so far no sign of any unrest.

"When we see the extent to which Macron is carrying this unfair pension reform through right to the end... we think we must not let up," warned Sophie Tissier, co-organizer of the protest.

With Macron seeking for now to rise above the fray, Prime Minister Edouard Philippe Friday insisted that the government would not abandon the plan, though he added it was prepared to bring it in gradually.

Philippe insisted he did not want "confrontation". But his comments failed to impress unions who want to keep the current pensions system of special regimes for public sector workers.

The CGT, one of the hardline unions at the heart of the movement, said that while the calendar may have shifted "nothing is changing in the aim of the government to smash our pension system based on solidarity and replace it with an individualist system".

"We call for the movement to intensify from Monday to make it clear that we want the plan to be withdrawn," said Laurnet Brun, the head of the CGT rail worker union.

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.

The Paris metro will remain severely disrupted with nine lines entirely shut, five only partially running and just the driverless 1 and 14 lines working normally.

There were also many cancellations on the international Eurostar and Thalys services.

Air travel, which has been less impacted by the strikes, was returning closer to normal with air traffic restrictions now dropped by civil aviation authorities.

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

Tourists in Paris may also face 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 has also cancelled its performances over the last days due to the strike.

Businesses also feared that the lack of transport would affect shopping activity on a key weekend for the consumer economy just two weeks before 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. — AFP