Service on three high-speed train lines in France was disrupted on Friday because of arson, the national railway company said, causing travel chaos on the day of the Opening Ceremony of the Olympics.

“A massive attack took place last night to paralyze the high-speed rail network,” the S.N.C.F. said in a statement. “Deliberate fires were set on the Atlantic, Northern and Eastern lines to damage our installations."

The company said traffic was “severely disrupted” on those lines. Many trains were canceled, it added, and advised travelers to postpone their trips if possible.

Patrice Vergriete, France’s transportation minister, said in a statement that “coordinated malicious acts” had targeted several of the country’s high-speed rail lines. This was expected to disrupt traffic and travel plans into the weekend, he said.

The S.N.C.F. said there was a “malicious act” around Arras, a town about 100 miles north of Paris, on the high-speed line between the capital and Lille. Another such act took place near Courtalain, a town about 90 miles southwest of Paris, on the lines connecting Tours and Le Mans to Paris, it said.

The company said that “a malicious act was thwarted” on the line that connects Paris to southeastern France.

Firefighters were responding to the two episodes, which happened at around 5:15 a.m., the company said. It warned that of cancellations and delays of 30 to 90 minutes.

The mood was already tense in Paris, where security has been tightening for weeks ahead of Friday night’s opening ceremony. Tens of thousands of police officers, joined by counterterrorism units and the military, have been deployed across the city to guard Olympic venues, tourist sites, train stations and street corners.

Weeks ago, the authorities cordoned off a section of the Seine on both banks to protect the thousands of athletes who will take part in the ceremony in a huge flotilla of boats and the hundreds of thousands of fans who will come to see it.