Moscow says it is expelling two Finnish diplomats in retaliation for Helsinki's decision to expel a similar number of Russian diplomats in April.
Russia's Foreign Ministry said on May 17 that it had summoned Finnish Ambassador to Russia Antti Helantera to inform him of the move, citing "Finland's confrontational course towards Russia."
Finland has provided arms to Ukraine, which Russia invaded in February, and lawmakers in Helsinki are expected later on May 17 to formally endorse joining the NATO security alliance.
Last month Finland expelled two staff members of the Russian embassy in Helsinki in reaction to Russia's aggression against Ukraine.
European nations have expelled hundreds of Russian diplomats since the unprovoked invasion was launched on February 24.