Russia has expelled a Swedish diplomat in what it describes as a response to a similar Swedish move.

The Russian Foreign Ministry said in a statement Tuesday that the move is a retaliatory measure to the "unfriendly action" against a Russian diplomat in Stockholm. It didn't identify either diplomat or give any further details. The ministry added that "Stockholm bears full responsibility for the consequences of this provocation."

Relations between Russia and Sweden have deteriorated amid strain over the Ukrainian crisis.

In March, the Swedish security service SAPO accused Russia of using as many as one-third of its diplomatic staff in the Scandinavian country for clandestine intelligence-gathering. SAPO said it stopped several attempts by Russia last year to obtain Swedish technology for military purposes.