Targeting remote locations far from the capital, the apparently coordinated attacks sought to cut off rail routes into the city from all directions. The fires were predominantly set in pipes containing critical signaling cables for the system known as the TGV.

There were no reports of injuries.

Fires were reported before dawn near the tracks on three separate lines, causing widespread disruptions. Another arson attempt, in the south in Vergigny, was thwarted by rail agents who scared off several suspects.

French authorities did not publicly comment on who might have carried out the attacks or why; none of them said the sabotage was directly related to the Games.

Prime Minister Gabriel Attal said intelligence services were mobilised to find the arsonists, whose attacks he described as “premeditated” and “calculated.”

The evidence indicates “a desire to seriously harm” the French people, said the CEO of national railway company SNCF, Jean-Pierre Farandou, who estimated the number of customers affected at 800,000.

“The places were especially chosen to have the most serious impact, since each fire cut off two lines,” he said.

The rail company said in a statement Friday evening that it would ensure transport for all Olympic delegations, without elaborating. It stepped up ground and air surveillance, including with 50 drones.

Prosecutors in Paris opened a national investigation, saying the crimes included property damage threatening the nation’s “fundamental interests” and could carry prison sentences of up to 20 years.

“Disturbing such a festival of peace with acts of violence can never be accepted and demands the most determined rejection,” German Chancellor Olaf Scholz said in Paris.

Two out of four trains carrying athletes to Paris on the western line were stopped hours before the opening ceremony, an SNCF official said.

Two German athletes who were on a Paris-bound train for the opening ceremony had to turn back in Belgium because of the closures, German news agency dpa reported.

Repairs were being made as police conducted forensic tests.

“We have to repair cable by cable, so it’s very meticulous work,” Farandou said.

French Transport Minister Patrice Vergriete said train traffic began to resume in the afternoon.

Rail officials said they expected most trains to be working again Saturday, with possible delays. Some disruptions were likely to continue into Sunday.

The attack occurred against a backdrop of global tensions and heightened security measures as the city prepared for the Games.

French authorities have said they foiled several plots to disrupt the Olympics.

In the capital, 35,000 police officers are being deployed each day for the Olympics, with a peak of 45,000 for the opening ceremony.

Paris has been the target of deadly terror attacks in the past decade, and some French officials saw the Games as a chance for the nation to heal from years of trauma.

– AAP