A French man has been arrested at the Polish-Ukrainian border after his car was found to contain an estimated 100kg in explosives, grenade launchers and assault rifles, French TV channel M6 reports.

The man is suspected of trying to smuggle the weapons into France, Russian publication RIA Novosti said.

He was arrested on May 21, France’s DNA news outlet reports, although news of his detention only emerged today.

The man has been in custody since, pending a possible transfer to France.

French publication 20 Minutes has described the man as a 25-year-old resident of Lorraine, with no previous criminal history.

His arsenal is said to have included explosives, three grenade launchers and multiple Kalashnikov assault rifles.

M6 reports the man’s home was found to contain explosive components and a T-shirt marked with the symbols of a right-wing group.

"Yes, we can confirm this happened, but it's SBU who's in charge of that," the press service told RT .

Ukraine’s security service SBU has declined to comment.