Train passengers were stuck for six hours in a tunnel outside Paris on Tuesday after their high-speed service suffered a power cut just minutes after departure, leaving them in sweltering heat, without electricity or working toilets.

The train bound for Barcelona became trapped in the tunnel in the Yerres area outside Paris. French rail operator SNCF said the power failure lasted only 10 or 15 minutes but the train was unable to restart because of its position. 

A new train was sent in to shunt the stalled carriages along, but without success.

Passengers were relocated through the tunnel to the working train in front accompanied by SNCF staff, firefighters and police, according to an AFP journalist, who said two passengers were looked after by emergency workers.

One tourist, 68-year-old Australian Heather Manton, expressed concern over her reservations in Barcelona and described the experience as "horrible".

The passengers were finally on the move by late afternoon.