Bulgaria, Estonia, Latvia, and Lithuania announced the expulsions on Friday.
Four European Union member states have expelled a total of 20 Russian diplomats amid its invasion of Ukraine.
Ten Russian officials have been ordered to leave Bulgaria, while Lithuania has expelled four diplomats and Latvia and Estonia have each expelled three.
"Latvia is expelling three employees of the Russian embassy due to activities contrary to their diplomatic status and in view of the ongoing Russian aggression in Ukraine," Latvian foreign minister Edgars Rinkēvičs said on Twitter.
Rinkēvičs added that the move had been coordinated with officials in the two other Baltic nations.
"Russia's military attacks on civilians, civilian targets, hospitals, schools, maternity hospitals and cultural property are war crimes and crimes against humanity," said Lithuanian Foreign Minister Gabrielius Landsbergis.
"Russian special services are actively involved in organising these crimes against the peaceful population of Ukraine," he added.
"We do not want the representatives of these structures to walk on our land and pose a threat to the national security of Lithuania."
Estonia's foreign ministry said the expelled diplomats were "directly and actively undermined Estonia's security and spread propaganda justifying Russia's military action."
Earlier on Friday, Bulgaria announced the expulsion of ten Russian diplomats for "activities not in accordance with the Vienna Convention on Diplomatic Relations".
It comes days after two more Russian officials were ordered to leave Bulgaria for spying and alleged "intelligence activities".
Earlier this month, Slovakia also expelled three Russian diplomats as part of an espionage investigation.
Russia's Foreign Ministry immediately said on Friday that it would announce an "appropriate response to all unjustified expulsions," according to a statement on Telegram.