Säpo chief Anders Thornberg says they have never seen anything like this before. And that it is because of the concentrated and collected propaganda from the so-called Islamic State terrorist group.
The thousands of people known to Säpo include those who support violent means to achieve Islamist politics. But very few have both the desire and the ability to carry out actual attacks.
During this year alone Säpö has received 6,000 tips from the public, and from surveillance, on Islamist extremists.
The extremists are cencentrated in the cities of Stockholm, Gothenburg, Malmö and Örebro, reports news agency TT.
Terrorism researcher Magnus Ranstorp says the new information matches his experience, and he's seen an increase since 2013, looking at social media.