Bucharest (AP) — Romania said on Monday it has expelled a Russian embassy official, in the latest of a wave of expulsions of Russian diplomats from European countries and counter-expulsions from Moscow.

Also Monday, Russia expelled an Italian naval attaché, the Italian Foreign Ministry said. That was in retaliation over Rome’s expulsion last month of two Russian diplomats after an Italian Navy captain was caught allegedly passing classified information to one of them.

Romania’s foreign ministry said the "activities and actions" of Alexey Grishaev, a deputy military attaché at the Russian Embassy in Bucharest “contravene the provisions of the Vienna Convention on Diplomatic Relations since 1961.”

Romanian authorities did not provide further details.

Russia's ambassador to Romania, Valery Kuzmin, told the Russian news agency Tass that the Romanian decision “is undeniably an unfriendly one,” and added that Moscow "reserves the right to take relevant measures in response.”

Last Friday, Estonia, Lithuania, and Latvia ordered the expulsion of a total of four Russian diplomats as an act of solidarity with the Czech Republic, where scores of diplomats have been expelled over the alleged involvement of Russian spies in a massive ammunition depot explosion in 2014.