Assault rifles, anti-tank grenade launchers and TNT were in a massive cache of weapons held by a man suspected of planning terror attacks in France.

In a new terror scare the French national's been arrested in Ukraine on suspicion of planning a string of attacks during the upcoming Euro 2016 championship.

Teams are starting to arrive for the competition which begins on Saturday.

Europe correspondent Catherine Field told Mike Hosking there are at least 90,000 police and security officials, but that's not all.

"Each team lives in a cordoned off zone. They're accompanied all the time by 17 police and two special ops soldiers so that type of security is big."

Sam Kiley from Sky News said the French national's been arrested in Ukraine.

"This weapons cache is extreme by anybody's standards. This is a huge amount of plastic explosive. Some of the weapons were supplied to him by agents working for the Ukrainian intelligence."

Ukraine's security service chief Vasily Gritsak said the man had many targets in his sights.

"The targets of the attacks, although it sounds strange, it is true and it was documented, are a Muslim mosque, a Jewish synagogue, a French tax office, highway patrol points and many other places. As I said 15 attacks were planned."

According to Ukraine, in that cache was 125 kilograms of TNT, five assault rifles, and two anti-tank grenade launchers.