Arsonists lighting fires in conduit points across France's high-speed rail network have disrupted the transport network hours before the Paris Olympics opening ceremony.

Train operator SNCF's chief executive, Jean-Pierre Farandou, said the attackers had started fires in "conduits carrying multiple (fibre-optic) cables" that carried "safety information for drivers" or control the motors for points.

"There's a huge number of bundled cables. We have to repair them one by one, it's a manual operation," requiring "hundreds of workers", he added.

Passenger services chief Christophe Fanichet said there were delays of 90 minutes to two hours on services between Paris and France's north and east.

"We ask people please not to come to the station, because if you haven't heard from us, your train won't be running," Mr Fanichet told reporters.

Mr Farandou said that railway workers doing night maintenance in central France spotted unauthorised people who fled when the workers called in police.

A spokesperson from the transport operator earlier told AFP the fires were a "massive attack on a large scale to paralyse the TGV [high-speed] network".

'Acts of sabotage'

The operator said that many routes would have to be cancelled and the situation would last "at least all weekend while repairs are conducted".

French Prime Minister Gabriel Attal called the attacks "prepared and coordinated acts of sabotage".

"Our intelligence services and law enforcement are mobilised to find and punish the perpetrators of these criminal acts," he wrote in a statement on X.

The incident is predicted to impact an estimated 800,000 passengers.

The attacks will affect its Atlantic, northern and eastern lines.

The south-eastern line was not affected as "a malicious act was foiled".

The attacks were launched as Paris prepares for the opening ceremony, with 7,500 athletes, 300,000 spectators and an audience of VIPs.

International Olympic Committee president Thomas Bach said he had "full confidence" in the French authorities despite the timing being so close to the Games.

"I don't have concerns," the German told the media at the Olympic Athletes' Village.

"We have full confidence in the French authorities."

Sports Minister Amelie Oudea-Castera condemned the vandalism.

"It's completely appalling," she told BFMTV.

SNCF urged passengers to postpone their trips and stay away from train stations.

Lengthy delays expected

Eurostar said its rail services between London and Paris had been disrupted, resulting in several cancellations and longer journey times.

"Due to coordinated acts of malice in France, affecting the high-speed line between Paris and Lille, all high-speed trains going to and coming from Paris are being diverted via the classic line today Friday 26 July. This extends the journey time by around an hour and a half," Eurostar said in a statement.

"Several trains have been cancelled."

At Paris's Montparnasse train station, dozens of passengers were waiting for more information about their trips after delays of 30 minutes to almost two hours were announced.

"Normal traffic is expected to resume on Monday, July 29," read one of the signs in the departure hall.

"We arrived around 7:00 am but we were told that we might not be able to leave before Monday," said 27-year-old student Jocelyn, who had planned to travel to Bretagne.

AFP