The man, who denies the allegations, was remanded in custody on Friday.
He is a Kazakh citizen in his 30s and lives in a municipality outside Östersund, according to court documents seen by The Local.
He was arrested in Östersund city centre on Wednesday over what first appeared to be a traffic offence.
Police then stepped up the investigation, first classifying the suspected crime as preparation of murder and next as conspiracy to commit a terrorism offence.
Swedish media report that police suspect that the man, who has lived in Sweden on and off with is wife and children in recent years, had intended to drive into people with his car.
Details were scarce on Friday, but the prosecutor said that they had already held lengthy interrogations and would continue to question the man.
There are no other suspects for now, but by definition a “conspiracy” offence must include another person, either known or unknown. Sweden's security police have not said why they suspect he is part of a conspiracy.