The news of the diplomats' expulsion was first reported on Monday evening by public broadcaster SVT, though Sweden’s Foreign Ministry and the Russian ambassador to Sweden have both declined to comment on the reports.
According to information shared with newswire TT, the deportation is a response to a “Swedish action” which happened some time ago, though it is not clear what exactly this action was.
“Sweden took a number of actions which affected several people, and then Russia chose this countermeasure,” a source with knowledge of the situation told TT.
Sweden and Russia have had a tense relationship for several years. Successive Swedish governments backed Ukrainian attempts to move closer to the European Union, to Moscow's annoyance. In 2013, Russian fighter jets carried out practice bomb attacks over Sweden.
In September this year, Sweden carried out its biggest military drill in 20 years, with overseas troops joining Swedes in the exercise which was named Aurora and came following an increase in military activity from Russia in the Baltic region.
In June, Sweden summoned Russia's ambassador after an SU-27 jet flew unusually close to a Swedish reconnaissance plane in international airspace above the Baltic Sea.
At the time of the Aurora drill, Russia's ambassador to Sweden Viktor Tatarintsev commented on the relationship between the two countries in an article published in Dagens Industri.
He said it was “high time” that Swedish-Russian relations improved, and that despite changes in Russia's government and “an enormous step forwards in openness and democracy”, the Swedish view of Russia had not improved and that bilateral relations were “hardly flourishing”.