Officials in Paris have increased security at public transport locations "as a precautionary measure" following the explosion in a St Petersburg underground tunnel on Monday.
In a statement, the interior ministry said: "Following the events in the St. Petersburg metro, and as a precautionary measure, Interior Minister Matthias Fekl has decided to redeploy security means in public transport across the Paris region.
"Amid an extremely high terrorism threat, the government continues to take measures to protect the French people."
The seven people were from Central Asian countries and investigators say they were recruiting for IS.
The bombing of a subway train in Russia has drawn condemnation from world leaders.
A blast has ripped through an underground train in Russia's second-largest city on Monday.