A quarter of the reports concerned burglary, illegal trespassing or illegal photography at protected sites.
The increase is partly due to more businesses being classified as essential to society, such as those in electricity, water and infrastructure. In many cases, people have taken photographs or entered an area by mistake.
139 cases have led to prosecution.
Säpo and the police are now working to get a better picture of the increase.
We need to work together to detect incidents that could involve possible sabotage or other hybrid activities from Russia or another foreign power, Säpo chief Charlotte von Essen said.
