PARIS (Reuters) - Passengers cannot yet book train tickets to and from three of Paris' main stations for July 26, when the Olympics opening ceremony will be held, France's state-owned railway operator said on Wednesday, as it opened ticket sales for the summer season.

SNCF, as the railway operator is known, said tickets for its signature TGV bullet trains as well as regional trains for that day to and from the Lyon, Austerlitz and Bercy stations will only be issued for sale once authorities "validate organisation conditions for the opening ceremony".