This is reported by TASS with reference to the Romanian Ministry of Foreign Affairs.
"The Romanian Foreign Ministry informs that the Romanian authorities have decided to declare persona non grata on the territory of Romania the assistant to the military attaché of the Russian Embassy in Bucharest," the foreign ministry said in a statement.
The ministry claims that "[the diplomat's] activities and actions are contrary to the provisions of the 1961 Vienna Convention on Diplomatic Relations."
On April 22, the Prime Minister of Slovakia Eduard Heger announced that Bratislava was expelling three Russian diplomats in connection with the situation in the Czech Republic.
The Russian Foreign Ministry said that Moscow will take retaliatory measures.
Also earlier, a number of other countries announced the expulsion of Russian diplomats, in particular, Latvia, Lithuania, Estonia, Poland.