France's high-speed railway hit by 'sabotage' during Olympics

A source close to the investigation told AFP the attacks were coordinated acts of "sabotage".

"This is a massive attack on a large scale to paralyse the TGV network," SNCF told AFP, adding that many routes will have to be cancelled.

"SNCF was the victim of several simultaneous malicious acts overnight," the national train operator said, adding that the attacks affected its Atlantic, northern and eastern lines.

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

Trains were being diverted to different tracks "but we will have to cancel a large number of them", the statement said.

The southeastern line was not affected as "a malicious act was foiled".

Around 800,000 passengers are expected to be affected over the weekend as the damage is heavy and labour-intensive to repair.

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.

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

Who are the culprits?

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

France's intelligence services were scrambling to determine the perpetrators of the sabotage, a security source told AFP. The arson method used resembled past attacks by extreme-left actors, the source added.

In September, arson attacks on conduits holding railway cables caused travel chaos in northern Germany, with a claim of responsibility posted to an extreme-left website.

Paris prosecutors opened a probe into a suspected bid to undermine "fundamental national interests," Paris prosecutor Laure Beccuau said in a statement.

The investigation will also probe suspected damage inflicted by an organised gang and attacks on an automated data processing system.

Olympics under heavy security

The attacks were launched as Paris was under heavy security ahead of the opening ceremony of the Summer Olympics, with 300,000 spectators and an audience of VIPs expected at the event.

The parade on Friday evening will see up to 7,500 competitors travel down a six-kilometre stretch of the river Seine on a flotilla of 85 boats.

It will be the first time a Summer Olympics has opened outside the main athletics stadium, a decision fraught with danger at a time when France is on its highest alert for terror attacks.

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 and refused to give her full name.

"We expected it to be a bit chaotic in Paris with the opening ceremony scheduled for this evening, but we didn't think it could be this bad," she said.