Ukraine's intelligence agency has thwarted a plot to attack the European Championship soccer tournament in France by arresting a heavily-armed Frenchman who wanted to cross into the European Union, officials said Monday.

The Ukrainian Security Service, or SBU, said it had followed the man since December and allowed him to purchase five machine guns, two rocket-propelled grenade launchers, 275 pounds of TNT, 100 detonators and other weapons. He also bought 20 balaclavas before he was arrested at the Yahodyn border crossing between Ukraine and Poland last month, authorities said.

The SBU "has managed to foil a series of 15 terrorist attacks which were planned to target France before and during" Euro 2016, said Vasyl Hrytsak, the security agency's chief.

The SBU didn't identify the man but said the suspect wanted to protest against his government's migration policies and the spread of Islam. It said he planned attacks on bridges, railways and other infrastructure for Euro 2016.

Extremist attacks are a major concern for French authorities as they prepare to host the monthlong tournament at stadiums in the Paris area and eight other cities from Friday through July 10. Islamic State extremists have threatened France during the tournament, but authorities haven't confirmed specific dangers.

France is deploying a 90,000-strong security force for the tournament, and President Francois Hollande said Sunday night that the threat of attacks won't stop it from being successful.

The Paris police prefect, Michel Cadot, declined to comment on the information from Ukraine, saying only that "there is no specific threat against any (Euro 2016) site."

Ukraine's intelligence agency had initially planned to keep a lid on the investigation, but decided to go public about the arrest after reports in international media, Hrytsak told national television.

French regional newspaper L'Est republicain identified the man as Gregoire Moutaux and said investigators raided his home in Nant-le-Petit near the eastern city of Nancy in late May. The source for the man's identity wasn't cited. French television network M6 reported that investigators found T-shirts of an extreme right group.

However, the Paris prosecutor's office, which handles terrorism cases at a national level, said no investigation had been opened yet.

Ukrainian authorities released photos of a fair-haired man, with his face blurred, holding various weapons, as well as a video of the arrest which showed SWAT officers dragging the man out of a white minivan and putting him on the ground of what looked like a parking lot with his face down.

The SBU said the Frenchman became known to the agency last year during his stay in eastern Ukraine, and where he was "trying to establish ties with Ukrainian troops under the guise of volunteering."

Ukrainian troops and Russia-backed separatists have fought in the east since April 2014, killing nearly 9,400 people. It wasn't immediately clear which side of the conflict the Frenchman had stayed with.

"The Frenchman spoke negatively about his government's migration policies, the spread of Islam and globalization," the SBU said. "He also said that he wanted to perpetrate acts of terror in protest."