A Thalys train from Amsterdam to Paris was attacked by a heavily armed man in August, but he was overpowered by passengers.
Brussels extends terror alert as United States issues travel warning
The French government has decided "to install gates for the Thalys in Lille and Paris before December 20," Royal, who is ecology minister but has responsibility for transport, said.
The high-speed Thalys service links Paris with Lille in northern France, the Belgian capital, Brussels, Amsterdam in the Netherlands and the western German city of Cologne.
Passengers boarding those trains do not currently have to pass through security checks, unlike for the cross-Channel Eurostar train services to Britain which have airport-style security.
Royal indicated that Belgian, German and Dutch authorities would also install security gates, although those countries have not yet confirmed that.
She said France was also considering bringing in a system of named tickets for Thalys passengers.
German business confidence unfazed by Paris attacks
France has tightened security at its borders and within the country following the militant attacks of November 13 on the French capital in which 130 people were killed.
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