The arrests came on the same day that Sweden became the 32nd member of NATO.
ADVERTISEMENTSweden’s Security Service said Thursday it had arrested four people on suspicion of preparing “terrorist offenses” with links to Islamist extremism and organised crime.
The service did not confirm whether any specific attacks had been planned, but in a brief statement it said it had “worked on the case for a long period of time.”
Sweden media reported there was a major police operation in Tyreso, south of Stockholm. Public broadcaster SVT said there was a “powerful explosion in a clubhouse" but it is unclear what caused the blast.
In August, Sweden's security service raised its terror alert to the second-highest level following a string of incidents where protestors publicly burnt the Quran.
Thursday arrests came on the same day that Sweden became the 32nd member of NATO, ending decades of post-World War II neutrality.