Sweden's security police service, Säpo, confirmed on its website on Thursday that Attunda district court in Stockholm had detained the man, who is suspected on "probable cause" of planning a terror act.
"I don't have more information than that, we're in an intensive stage of the investigation," press officer Fredrik Milder told the TT newswire.
According to court documents obtained by Swedish tabloid Aftonbladet, the man is 20 years old, based in a municipality north of Stockholm, and was arrested by a prosecutor on Monday.
He is suspected of having committed the offence in January this year and according to the Expressen tabloid he was first questioned two weeks ago.
Sweden's Prosecution Office (Åklagarmyndigheten) confirmed to The Local that the man had been detained, but was unable to offer more information about the ongoing investigation.
"I can't tell you more than that he has been detained," said press officer Karin Rosander.
Sweden raised its terror alert to 'high' for the first time in history in November 2015 in the wake of the attacks in Paris that left 130 people dead and a separate suspected plot on Swedish soil.