Russia on Tuesday lashed out at Stockholm and confirmed it had expelled a Swedish diplomat in retaliation for the Scandinavian country turfing out one of Moscow's diplomats.
Russia's foreign ministry said in a statement that it had recently declared a Swedish diplomat "persona non grata" in a tit-for-tat move after the "hostile actions by the Swedish authorities".
"The responsibility for the consequences of this provocation lies squarely with Stockholm," the statement said.
Sweden said Monday that Moscow had kicked out one of its diplomats as "a response" to an earlier expulsion of a Russian diplomat by Stockholm.
The Russian diplomat was expelled because of actions "not in line with the Vienna Convention" which governs diplomatic relations, a Swedish foreign ministry spokesman said, providing no further details on the nature of the Russian's actions nor the exact timing of that expulsion.
Tensions between Moscow and Stockholm have risen against the backdrop of the worst East-West standoff since the end of the Cold War over the crisis in Ukraine.
Swedish Defence Minister Peter Hultqvist said in June that Sweden, a non-NATO country, was stepping up its military capabilities and exercises with the alliance amid concerns over Russia's military resurgence.
Sweden and the rest of the Baltic region have become increasingly jittery amid signs of more assertive Russian behaviour, including Russian planes regularly skirting or violating the national air space of neighbouring countries.
And in October 2014, Sweden launched a massive hunt for a foreign submarine, suspected to be Russian, in the Stockholm archipelago over an eight-day period.
The military subsequently confirmed that "a mini submarine" had violated its territorial waters, but was never able to establish the vessel's nationality.