Russia accused Finland of pursuing a "confrontational" policy towards Moscow.
Russia said on Thursday it was expelling nine diplomats from Finland, Russia's neighbour and NATO's newest member, in a tit-for-tat measure.
Finland said last month it was expelling nine Russian diplomats, accusing them of working on intelligence missions.
Russia had also decided to close the Finnish consulate in St Petersburg, the Russian Foreign Ministry said, accusing Finland of pursuing a "confrontational" policy towards Moscow.
"It was noted that the currently discussed parameters of Finland's entry into NATO pose a threat to the security of the Russian Federation, and encouraging the Kyiv regime to go to war and pumping it with Western weapons amount to clearly hostile actions against our country," the Russian statement said.
"This line of the Finnish authorities cannot remain unanswered."
Finnish President Sauli Niinisto called the measures "a harsh and unsymmetrical response to Finland's expulsion decisions".
He said Finland was preparing, in response, to close the Russian consulate in Turku.
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