ISIS in Sweden: Islamist Extremists on the Rise in Nordic Nation, Spy Chief Says

Sweden has witnessed a surge in Islamist extremists: from 200 less than a decade ago to "thousands," in 2017, the Scandinavian country's spy chief said Friday.

"We have never seen anything like this before," Anders Thornberg, chief of the Swedish Security Service (SAPO), told the country's TT news agency.

"This is the 'new normal'...It is a historic challenge that extremist circles are growing," he added.

One of the primary challenges facing security services in Sweden, Thornberg said, is that more extremists are aligned in their views because of Islamic State group (ISIS) propaganda.

"We used to have different circles. We had radicalized [people] from North Africa, the Middle East and Somalia, but they were all separate," he said.

SAPO said most of the militants were based in the cities of Stockholm, Gothenburg, Malmö and Örebro, although only a few of the thousands documented were willing to and capable of carrying out an attack on Swedish soil.

The country's intelligence agency also has been inundated with tip-offs relating to extremism, tripling from a monthly average of 2,000 in 2012 to 6,000 in 2017.

SAPO previously estimated that around 300 Swedish nationals have traveled to Iraq and Syria to fight for radical Islamist groups.

Thornberg said some Swedish national security threats may not be detectable, as militants no longer need months to prepare for a high-tech assault. "Today, if you decide to act, you maybe buy two knives or hire a truck and drive into a crowd," he said.

Read more: ISIS fears mean Finland, the world's safest country, is raising its threat level

The spy chief's comments come two months after a 39-year-old Uzbek national plowed a truck into shoppers on a busy central Stockholm street, killing five and injuring 15. Authorities said the attacker had sympathies with ISIS. He remains in detention.

Neighboring Finland, which the World Economic Forum classified as the safest country in the world in a report published in April, raised its threat level from 'low' to 'elevated' on Wednesday, citing small numbers of people inspired by jihadist groups such as ISIS. The Finnish Security Intelligence Service said it had obtained knowledge of extremism-related plans being made in the country.