Sweden's security police Säpo carried out the raids in coordination with the national police and National Operations Department (NOA) across multiple locations on Thursday morning, including the Lilla Edet and Ale municipalities in Västra Götaland.
The man, who is 22 years old and stateless according to court documents seen by The Local, is being held on suspicion of preparation or conspiracy to commit a terrorist crime, as well as aggravated weapons crimes. By Friday morning, he was still in police custody and no further suspects had been detained.
His lawyer said that the man denied the charges, but could not comment any further.
According to Säpo, the criminal preparations had been ongoing for some time.
“We can see that there are links to international terrorism, but at the moment we can't say which countries,” said Säpo press secretary Sofia Hellqvist.
Hellqvist also declined to comment on any times or locations for the suspected crime, for example if it related to Sweden or another country.
Sweden's national terror threat level remains unchanged at three on a five-point scale.
In November, the UK raised its own assessment of the threat level in Sweden, reflecting what it referred to as an “increased threat” of terrorist attacks.
When asked by the TT newswire if this had any connection to this week's operation, Säpo's Hellqvist said: “We cannot comment on what other countries do with their warnings. But we don't see any connections at this time.”