Moscow said Monday it was expelling an Italian diplomat in response to the "unfriendly" removal of two Russian officials from Rome in March over an espionage scandal.

The foreign ministry said it had summoned Italy's ambassador and informed him that Russia was declaring "persona non grata" Rome's naval attache in Moscow, who would have 24 hours to leave the country.

Rome announced late last month it was expelling the two Russian officials after an Italian navy captain was caught by police selling confidential military documents to a Russian embassy official.

The navy officer, Walter Biot, worked in the office of the Chief of the Defence Staff, and reportedly passed on dossiers to the Russians in return for 5,000 euros (around $6,000).

Rome on Monday immediately condemned the expulsion, describing it as "unfounded and unjust because it is in retaliation for a legitimate measure taking by the Italian authorities in defence of their own security".

Recent weeks have seen a wave of expulsions of Russian officials from European countries and the United States over claims of hacking and espionage.

Tensions have spiralled in particular with the Czech Republic after Prague accused Russian military intelligence of being behind a deadly explosion at an ammunition depot in 2014.

Prague expelled 18 Russian diplomats over the allegations and Moscow retaliated by kicking out 20 Czech embassy staff.

Romania said Monday it would expel a Russian diplomat in solidarity with the Czech Republic, following similar decisions taken by Slovakia and the Baltic states.