Arsonists carried out overnight attacks on the country's high-speed train network, causing major travel disruption ahead of this evening's Paris Olympics opening ceremony.

With the games under way amid an unprecedented peacetime security operation, state-owned railway operator SNCF said vandals used explosive devices to set off fires which damaged signal boxes along three lines connecting the capital with cities such as Lille in the north, Bordeaux in the west and Strasbourg in the east.

It had said timetables would be severely impacted all weekend and urged all travellers to postpone their journeys - but added in a later statement that customers will be contacted by text message and email to "confirm their train movements".

Paris Olympics: Eurostar affected by 'acts of malice'

SNCF said 1,000 maintenance workers had been mobilised to monitor the network, with 40 railway police teams and 50 drones supporting them.

It read: "In coordination with the forces of law and order, surveillance of the network has been stepped up on the ground and in the air, using both human and technical resources."

On the eastern line, which connects Paris to Strasbourg, rail traffic is expected to resume as normal from 6am on Saturday.

On the northern line, connecting Paris to the Belgian border and the Channel Tunnel, 80 percent of high-speed trains are running, although delays vary between one and two hours.

Towards Brittany and the south east area, two trains out of three are expected to be running from Saturday.

Eurostar asked passengers to cancel their trips if they can, amid ongoing disruption to its services, just as many families plan to head off on their summer holidays.

One in four Eurostar trains will be cancelled on Friday and over the weekend following "coordinated acts of malice in France", the company added.

Travellers at St Pancras international terminal had been informed there was a problem with overhead power supplies in France.

Most of the Team GB athletes were arriving at the games via Eurostar, but the British Olympic Association confirmed only two athletes were due to arrive on Friday and had been subject to only minor delays.

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The disruption has particularly affected Paris's major Montparnasse station.

Services between France and Germany have also been affected by cancellations and delays.

France's intelligence and security forces have been "mobilised" in response to the arson attacks, according to Prime Minister Gabriel Attal.

He said: "What we can see is that this operation has been planned, coordinated, that key points have been targeted which shows a kind of knowledge of the (train) network. They knew where to hit."

Speaking to Sky News, the country's sports minister Amelie Oudea-Castera said of the arson attacks: "I condemn them extremely strongly. It's just unacceptable.

"It's probably a large-scale sabotage with some malicious acts, probably coordinating."

When pressed if it could be the work of terrorists or even another nation, she said "possibly" - before pointing out it could also have been caused by protesters.

She added: "At the moment, we don't know. It could be French people. What's clear is that they are playing against the athletes."

Transport minister Patrice Vergriete said in a post on X that he "firmly condemns these criminal incidents".

British Prime Minister Sir Keir Starmer has urged people going to Paris for the Olympics to heed the travel advice.