The demonstrators, in Malmö to take part in the European Social Forum, unfurled a banner reading “Made in Malmö, Kills in Iraq.” Some of the protesters lay on the ground, playing dead.
The Swedish company Aimpoint, whose headquarters are located a few kilometres from central Malmö, manufactures red dot sights for guns sold to the US army, among others.
The demonstration was organized by a network of activists called European Peace Action.
Some of the activists, including many Swedes and Germans, climbed the fence surrounding the company grounds.
A Swedish police spokesman told AFP six people had managed to enter a factory on the grounds, but Swedish and German police had removed them from the scene after a few minutes.
The protest lasted about an hour without any other incidents