Ukraine’s security service detained a French national at the Polish-Ukrainian border who was in possession of a large cache of weapons. Authorities said that he is involved in a series of plots to attack the Euro 2016 football championship that starts in France later this week.

French media identified the man as Gregoire M. and reports said the 25-year-old was arrested on May 21. He was being held by Ukrainian authorities who suspect him of trying to acquire more weapons.

The Ukrainian border service confirmed the arrest to the Russian news agency, RIA Novosti, saying: “Yes, we can confirm this happened, but it's SBU [Security Service of Ukraine] who's in charge of that.”

SBU chief Vasyl Hrytsak said the man had been planning nearly 15 attacks and was driven by ultra-nationalist views. The man was in possession of five Kalashnikovs, two anti-tank grenade launchers, at least 5,000 rounds of ammunition, 100 detonators and 125 kg (275 pounds) of TNT, Hrytsak reportedly said.

Reports said his home in the northeastern region of Lorraine in France was searched where French police found explosive components and a T-shirt bearing symbols of a far-right group. He had no previous criminal record and was being monitored by the SBU since December 2015.