The operation during Friday evening was carried out together with the police. Säpo does not want to answer what type of measures have been taken and whether anyone has been detained.
According to sources for SVT, the police have blocked off the entrance to an apartment building.
The four people arrested on Thursday are in custody, suspected of preparation for terrorist crimes and serious weapons crimes.
Säpo has told us earlier today that the operation in Tyresö has connections to IS in Somalia.
Säpo after the strike last Thursday in Tyresö: ”Links to IS in Somalia”:
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Hear Fredrik Hallström, operations manager at Säpo, about the effort in Tyresö Photo: SVT