The man, who is in his 20s, was previously detained in absentia and has now been requested to be handed over to Sweden.
Three more people are suspected of involvement in the case, prosecutor Viktor Wetterö said in a press release.
A man in his 20s is now being held in custody on probable cause on suspicion of two counts of aggravated robbery, attempted aggravated robbery and attempted aggravated rape. A man in his mid-20s was arrested on Thursday as a reasonable suspect for the same crime.
The fourth person, a boy under the age of 18, was arrested on Tuesday as a reasonable suspect and has now been released on bail - but remains a suspect.
The crimes were committed against four people, all over 80 years old, over two weeks in late December and early January.
