They are suspected of selling a rocket powered firearm and an AK-47 to an undercover Danish agent in Copenhagen, who was helping the US Drug Enforcement Agency. It suspects the Swedes are involved in an operation with links to Colombian terrorists.
The mastermind behind the operation is said to be a Swede, and is already in custody in the United States.
Officers there believe he was selling weapons to the Columbian Farc guerillas, in exchange for cocaine. Drugs are also thought to have been the payment for the latest firearm delivery, reports news agency TT.