The Finnish Security Intelligence Service (Supo) warns that more than 200 convicts jailed for terrorism crimes will be freed from Western European prisons within the next few years.
"While in prison, these people may not necessarily have changed the way they think, unfortunately," Supo Director Antti Pelttari said. "What's more, they may have created networks with organised crime."
According to Pelttari, who spoke at a security seminar at Parliament on Wednesday, there are currently no factors in sight which would lower the threat of terrorism.
"Now that the extremist organisation ISIS is losing ground, individual terrorists and terror networks are looking for a new purpose," he said.