Estonia's foreign ministry said Wednesday Russia had expelled its St. Petersburg consul, in what Tallinn called a tit-for-tit response to an unspecified move by the Baltic nation.
Consul Franek Persidski "is already in Estonia", foreign ministry spokeswoman Minna-Liina Lind told AFP.
"It is a counteraction by Russia to a similar step taken earlier by Estonia," she added without providing details.
But Russia's RIA Novosti news agency spoke of speculation that the expulsion was over Tallinn's refusal to issue visas to a handful of Russians planning to participate in a roundtable there last month.
Relations between Moscow and Tallinn have been fraught with tension since Estonia broke free from the crumbling Soviet Union in 1991, joining both the EU and NATO in 2004.
Last year an ex-senior Estonian state security official was found guilty of spying for Russia and sentenced to 16 years behind bars.
The then 44-year-old Aleksei Dressen was found guilty of treason for illegally funnelling classified information to Russia for years after the fall of the Iron Curtain.
He is the second high-level security official in Estonia caught spying for Russia in recent years.
In 2009, Herman Simm, a senior Estonian defence ministry official was also jailed for selling NATO secrets to Russia.