Russia said on Monday it was downgrading diplomatic relations with NATO member Estonia, accusing Tallinn of "total Russophobia".
The Russian Foreign Ministry said it had told the Estonian envoy he must leave next month, and both countries would be represented in each other's capitals by an interim charge d'affaires instead of an ambassador.
It said this was in response to an Estonian move to reduce the size of the Russian embassy in Tallinn.
"In recent years, the Estonian leadership has purposefully destroyed the entire range of relations with Russia. Total Russophobia, the cultivation of hostility towards our country have been elevated by Tallinn to the rank of state policy," it said.
Estonia and its Baltic neighbours Latvia and Lithuania have been among a group of NATO allies arguing strongly for Germany to provide its Leopard battle tanks to boost Ukraine in fighting off Russia's invasion.
Estonia joined other Ukrainian allies last week in sending more weapons of its own.
Commenting on the downgrading of ties, Russian Foreign Ministry spokeswoman Maria Zakharova said: "The Estonian regime has got what it deserved."