Paris police boosted security on the city's transport system in the light of Monday's terror attack on the St Petersburg Metro system that left 14 dead and over 40 injured.
Some 140 extra gendarmes military police were deployed on the network, to reassure the capital's commuters.
Another move taken by police chief Michel Cadot was to allow officers to search passengers' bags if they have reason to be suspicious, whether its on Metro or RER lines, or in stations.
Cadot said the measure was taken at the request of the French government which had asked authorities in Paris to step up security measures.
Normally police must have a precise motivation or reason before they can search someone's bags, usually related to a crime that had been committed.
But from now on the police can control and search whoever they want, without having to justify it.
Police say the measure is taken regularly and must be renewed every 24 hours for as long as the police want to impose it.
Paris has been on high alert for terror attacks since jihadist gunmen and bombers killed 130 people in November 2015.