Several Russian diplomats have been expelled from Poland and a number of Polish envoys have left Russia after Moscow countered what it called “an unfriendly and unfounded step”.

The Russian foreign ministry did not say on Monday 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 quit 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 driven out amid media reports he was a spy.

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

Ties between Russia and Poland, which for decades was under communist rule and dominated by Moscow after the second world war, 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.