Russia's foreign ministry said on Friday it had ordered Latvia's envoy to leave the country within two weeks following a decision by Riga earlier this week to expel Moscow's ambassador.
The ministry said it had summoned the Latvian charge d'affaires to protest over Riga's decision to downgrade relations with Russia.
Latvia said on Monday it had acted out of solidarity with its Baltic neighbour Estonia, which also expelled its Russian envoy, prompting a tit-for-tat response from Moscow.
In its statement, the Russian ministry said it saw "solidarity" only in the Baltic states' "total Russophobia and a desire to be the initiator of hostile steps towards Russia, which are encouraged by the United States and some other countries that are unfriendly to us".
The ministry also criticised what it said were measures to restrict the Russian language in Latvia and the destruction of Soviet-era memorials and cultural legacy. Latvia is home to a large ethnic Russian minority.
The three Baltic states, which also include Lithuania and which were all once part of the Soviet Union, have been among a group of NATO allies arguing strongly for more Western tanks to be sent to Ukraine to help it fight Russian forces.
Lithuania expelled its Russian envoy in April and downgraded its diplomatic representation.