A major fire in the Paris suburbs paralysed traffic in and out of the city's Montparnasse train station on Friday, just as scores of French and foreign travellers head on their holidays.

Photos and videos posted on Twitter showed a massive plume of smoke rising into the skies from an electrical centre run by the national transport network in Versailles, southwest of the city.

The blaze shut down departures and arrivals at Montparnasse in southern Paris, the main station connecting the capital to west and southwest France.

"Our technical teams are dealing with the situation," rail operator SNCF said on Twitter.

The shutdown came just as many Parisians were heading Friday to the beach or the countryside to start their August vacations.

Montparnasse station was the scene of similar transport chaos almost exactly a year ago, when a giant signalling failure caused three days of heavy disruption.