Russia said on Monday (November 17) that several of its diplomats had been expelled from Poland, and that a number of Polish diplomats had left Russia, after Moscow retaliated against Warsaw. On Saturday, Germany reported that one of its diplomats had ordered to leave the Russian capital, following a German decision to expel a Russian diplomat working in Bonn.

The Russian Foreign Ministry did not say why the Russian diplomats had been expelled, and the Polish embassy declined immediate comment.

Diplomatic sources said four Polish diplomats had left the country on Sunday. “The Polish authorities have taken an unfriendly and unfounded step,” Russia’s Foreign Ministry said in a statement.

“In connection with that, Russia has undertaken adequate measures in response and a number of Polish diplomats have already left the territory of our country for activities incompatible with their status.”

The diplomatic sources told Reuters three Polish military attaches and one employee of the political section had left Russia on Sunday after being given 48 hours to leave the country on Friday.

Germany said on Saturday one of its diplomats had been expelled from Moscow after a Russian diplomat working in Bonn was expelled amid media reports he was a spy.

“We regret this unjustified action and expressed that to the Russian government,” a German official said in a statement late on Saturday after Der Spiegel reported the German was expelled in retaliation for the Russian’s expulsion.

The German diplomat, a woman, worked at the German embassy in Moscow. The Russian diplomat concerned had been under observation by Germany’s anti-espionage agency, the Office of the Protection of the Constitution, for several months, Der Spiegel said.

Protest against NSA espionage. Berlin, August 2014.

Protest against American espionage. Berlin, August 2014. [Markus Winkler/Flickr]

Relations between Moscow and European Union member states have been strained by the crisis in Ukraine and by EU sanctions imposed after Russia annexed the Crimea peninsula from Ukraine.

Ties between Russia and Poland, which for decades was under communist rule and dominated by Moscow after World War Two, have historically been difficult and Warsaw has been one of the fiercest critics of Russia over its role in Ukraine.

Earlier this year, the Polish government cancelled events intended to celebrate bilateral cultural ties in 2015, and last month withdrew accreditation for a Russian journalist working in Warsaw, acting on a request of the Polish internal security agency.

Der Spiegel noted that other comparable cases of diplomats being expelled in the recent past had not led to retaliation.

In July, Germany told the CIA station chief in Berlin to leave the country in response to questions raised about U.S. intelligence activity in Germany, including the discovery of a suspected U.S. spy in the Defense Ministry.