The rail operator told passengers to expect delays of up to four hours on the TGV network, which carries the bulk of traffic between major French cities, as engineers repaired the damage.
Bernard Thibault, head of the CGT union, condemned the attacks and suggested they may have been designed to discredit the strike movement.
"If this is indeed an act of sabotage ... then it is an inadmissible act that is aimed above all at bringing discredit on the profession," he told Europe 1 radio.
Managers from SNCF and the Paris metro operator RATP have been meeting unions and state representatives to discuss modifications to the government's plan to end early retirement rights for transport and energy workers.
Salary rises and top-up pension schemes have been suggested, and SNCF management has said a 90 million euro a year financial package is available if the strikers return to work.
The negotiations which began on Wednesday were scheduled to run into December, but Nicolas Sarkozy, the French president, has called on remaining strikers to return to work while details of a possible deal are discussed.
On Tuesday, he broke his week-long silence on the strikes, saying he would not surrender or water down his plans, as the system needed to be changed "to meet the challenges imposed on it by the world".
"These reforms have been too long in coming... After so much hesitation, so much procrastination, so many backward steps, we will not surrender and we will not retreat," he said.
The showdown over pensions is the biggest challenge Sarkozy has faced since taking office in May, and his government fears its credibility will be destroyed if it gives in to the unions.
|Civil servants and students have also |
taken to the streets [AFP]
Laurence Parisot, the head of the employers' federation MEDEF, compared the strike to an earthquake.
"The economic cost is incalculable and likely to be gigantic. So many customer meetings have been missed; so many business opportunities have been lost; who knows the number of foreign investors who have given up some venture or another here?"
An opinion poll published in Le Figaro
newspaper on Wednesday gave Sarkozy a boost, saying 68 per cent of people thought that the transport strike was not justified.
The last time a government tried to reform the so-called special pension regimes was in 1995, but it was forced to backtrack in the face of nationwide stoppages and broad public sympathy for the strikers.
Meanwhile, teachers, postal workers and civil servants returned to work after a one-day strike to protest against the government's economic programme. They have promised further stoppages in the months ahead.