The coordinated sabotage took place as France mounted a massive security operation involving tens of thousands of police and soldiers to safeguard the capital for the sporting extravaganza, sucking in security resources from across the country.

Société nationale des chemins de fer français  (SNCF), the state-owned railway operator, said vandals had damaged signal boxes along the lines connecting Paris with cities such as Lille in the north, Bordeaux in the west and Strasbourg in the east. Another attack on the Paris-Marseille line was foiled.

There was no immediate claim of responsibility. Two security sources said the modus operandi meant initial suspicions fell on leftist militants or environmental activists, but they said there was not yet any evidence.

Prime Minister Gabriel Attal declined to speculate about the possibility of such groups being behind the sabotage.

"What we know, what we see, is that this operation was prepared, coordinated, that nerve centres were targeted, which shows a certain knowledge of the network to know where to strike," he said.

The coordinated strikes on the rail network will feed into a sense of apprehension ahead of the Olympics opening ceremony in the heart of Paris later today. Operations at the Basel-Mulhouse airport on France's border with Switzerland were briefly suspended due to a bomb alert.

International Olympic Committee President Thomas Bach said he had full confidence in the French authorities. "I don't have concerns," he told reporters at the Olympic Village.

More than 300 000 spectators are expected to line the banks of the River Seine when the athletes' parade through the heart of Paris on a flotilla of barges and riverboats, part of an extravagant opening ceremony that will be watched by a global audience.

France is deploying 45 000 police, 10 000 soldiers and 2 000 private security agents to secure the Games' opening ceremony. Snipers will be on rooftops and drones keeping watch from the air.

But while the capital is locked down for the opening ceremony, security elsewhere in the country is lighter.

MANY STRANDED

The TGV high-speed rail attacks left hundreds of thousands of people stranded at stations.

Eurostar's high-speed services linking London and Paris were forced onto slower lines while Germany's Deutsche Bahn warned of disruption to long-distance services.

The SNCF urged all travelers to postpone their journeys. Repairs were underway but traffic would be severely disrupted until at least the end of the weekend.

At the Gare de L'Est, Xavier Hiegel, 39, said he was just trying to get home for the weekend and could not believe that people would want to harm the Olympics.

"The Games bring jobs so this really is nonsense. I hope the people responsible will be found and punished," he said.

The attacks hit signaling installations on the Atlantic, Northern and Eastern high-speed lines with fires set off by explosive devices, the SNCF said.

SNCF Chief Jean-Pierre Farandou said some 800 000 customers had been impacted ahead of a busy weekend for French holidaymakers. Thousands of rail staff had been deployed to repair the damage.

"This attack is not a coincidence, it's an effort to destabilise France," Valerie Pecresse, president of the Paris region, told reporters.

Paris 2024 said it was working closely with the SNCF to assess the situation. The attacks will make it tougher for people traveling to Paris from other areas of France.

"It's a disaster," said Parisian Brigitte Dupont. "Today is the opening of the Olympic Games, a huge event that was supposed to be magnificent, and this is spoiling people's joy."

--Reuters--