Russian Foreign Ministry said on Friday it had ordered Latvia's envoy to leave the country within two weeks following a similar decision by Riga earlier this week.
The ministry said it had summoned the Latvian charge d'affaires to protest over Riga's decision to downgrade relations with Russia.
Latvia has said it acted out of solidarity with Estonia after Tallinn also ordered out Russia's envoy. The three Baltic states, which also include Lithuania, have been among a group of NATO allies arguing strongly for more Western tanks to be sent to Ukraine.