It added there were no indications that any attack was planned for the next few days.
“Preparations for the suspected crime have been ongoing for some time,” the security police said.
The terrorist threat level remained unchanged at three on a scale of five.
Security police declined to give further comment.
In April last year Uzbek asylum seeker Rakhmat Akilov killed five people when he mowed down pedestrians with a truck on a busy Stockholm street. He is on trial and has confessed to driving the truck.
More about: #Sweden
