France completes rail repairs after arson attack

France's national rail operator on Sunday said it had repaired damage caused by saboteurs that paralysed the train network hours before the Olympics opening ceremony, and normal services would resume on Monday.

Train traffic on the main line west out of Paris was already "practically normal" and "three out of four" high-speed TGV trains were running on the main line north from the capital, "without any increase in travel time from now on", operator SNCF said on Sunday.

It remains unclear who carried out the three attacks on strategic points of the rail infrastructure overnight on Thursday to Friday, or if they were deliberately timed to disrupt the Games' opening spectacle later on Friday.

Tens of thousands of rail passengers struggled through two days of cancelled and delayed trains on Friday and Saturday, when 800,000 travellers were due to leave for their summer holidays.

"Thanks to the exceptional efforts of SNCF Network staff, who worked non-stop since Friday morning, repairs are now fully completed on all the high-speed rail services affected by the sabotage attacks," the operator said.

"Tests have been conclusive and the train lines are now able to function as normal.

"There will be no more disruption from Monday morning onwards," it said.

No group has claimed responsibility for the meticulously planned night-time attacks. Maintenance workers thwarted a fourth.

A source close to the Paris judicial authority, which has launched an investigation, said the attacks had all been carried out by "the same entity".

A statement signed by "an unexpected delegation" was sent to several news media outlets expressing support for the sabotage and criticising the Olympic Games as being a "celebration of nationalism" and the oppression of peoples by nation states.

But sources close to the investigation said it was simply a message of support, rather than a claim of responsibility per se, gave no details of the attacks and contained "nothing particularly serious".

"We have uncovered a certain number of elements that allow us to think that we will soon know who is responsible for what clearly did not sabotage the Olympic Games but did sabotage part of the holidays of the French people," Interior Minister Gerald Darmanin told France 2 television on Saturday.

French authorities are on high alert for a potential terrorist attack during the Games, which run until August 11.

Tens of thousands of police and soldiers have been placed on security duties during the Olympics.