Bulgaria's Ministry of Foreign Affairs has said it has declared one Russian diplomat persona non-grata on 29 April. After the news of the diplomat's expulsion was released, Russia said it would respond and enact retaliatory measures.
Bulgaria has also decided to ask for assistance from Russian law enforcement agencies in the investigation into military depot blasts, the Foreign Ministry said.
"The Bulgarian Foreign Ministry declared another Russian diplomat persona non grata and appealed to the law enforcement agencies of Russia with a request to provide comprehensive assistance to the Bulgarian authorities in the investigation of the explosions in the Bulgarian arms depots, destruction of evidence in a fire and the poisoning of three Bulgarian citizens in order to establish the perpetrators and bring them to justice," the ministry said.
Bulgaria’s Foreign Minister Ekaterina Zaharieva asked for Russia's full cooperation on the suspected four explosions at arms depots in Bulgaria and alleged attempts to poison Bulgarian arms trader Emilian Gebrev.
"Deputy Prime Minister and Foreign Minister Ekaterina Zakharieva had a thorough and serious conversation with the Russian ambassador in Sofia ... Bulgaria wants to maintain equitable and mutually beneficial relations with Russia, and in this context it insists on active and effective cooperation from the Russian side in the investigation into incidents on our territory," the Bulgarian Foreign Ministry said in a statement.
Sofia reserves the right to respond to Moccow, and calls on it to cease actions that are "incompatible with the Vienna Convention on Diplomatic Relations," the foreign ministry continued.
Bulgarian media reported that six Russian citizens were suspected of being involved in the blasts at factories and arms depots - three of whom were charged with the attempted murder of Bulgarian businessman Emilian Gebrev. Bulgarian prosecutors are now looking into four alleged explosions at arms depots between 2011 and 2020.
On 17 April, Prague announced that 18 Russian diplomats would be expelled from the Czech Republic because they were suspected of working for Russia's special services. Prime minister Andrej Babis explained that suspicions were aroused because it was believed that Russian military intelligence officers were behind the 2014 explosion in Vrbetice, which killed two Czech nationals.
Moscow retaliated by expelling 20 Czech diplomats, prompting Prague to order more diplomats out of the country in response.