French broadcaster M6 reported on Friday that the 25-year-old was arrested by Ukrainian border guards with an arsenal of weapons and explosives including rocket launchers and Kalashnikov assault rifles in his vehicle.
A spokesman for the Ukrainian Border Guard, Oleg Slobodyan, confirmed the arrest. A spokeswoman for Ukraine's SBU security service declined to comment.
The man, who is currently being held by Ukrainian authorities pending a possible extradition request from Paris, was planning an attack in France, M6 reported.
Security officials in Europe are on high alert after gunmen killed 130 in Paris in November last year and suicide bombers blew themselves up at Brussels airport and on the metro in March, killing 32.
The United States on Tuesday warned its citizens of possible further attacks in Europe, saying targets could include the UEFA Euro 2106 soccer championship in France beginning next week.