Swedish security police (SAPO) said on Thursday they had arrested a person suspected of preparing or inciting a terror crime, and of illegal weapons possession.
"The person has carried out preparations for the suspected terror crime for some time and there are international connections," SAPO said in a statement.
SAPO tweeted the news, saying: "A person has been arrested suspected of, among other things, preparation of a terrorist offence."
SAPO said they had carried out raids in western Sweden following extensive information-gathering. Several people were being interviewed in addition to the person arrested. The identity of the person being held has not been released.
Police spokesman Gabriel Wernstedt declined to say which countries the case was linked to, but said the operation had no known links to a gun attack on a Christmas market in Strasbourg on Tuesday. French police are still hunting a man suspected of killing at least two people in that attack.
Sweden, where an Uzbek asylum seeker mowed down pedestrians with a truck and killed five people in Stockholm last year, has kept its terrorist threat level unchanged at elevated, which is a three on a scale of five.