Montenegro on September 29 ordered the expulsion of six Russian diplomats who worked for the Russian Embassy in Podgorica amid an investigation into alleged spying.
The six were declared personae non gratae due to "activities that are contrary to the Vienna Convention on Diplomatic Relations," the Foreign Ministry tweeted.
Moscow retaliated by closing its consulate in Montenegro "indefinitely," Russia's Embassy said in a statement.
The embassy said in a statement that due to "hostile actions by Montenegrin authorities toward the Russian embassy in Montenegro," the work of the consular department in Podgorica has been "suspended indefinitely."
Authorities earlier searched several homes and other locations as part of an investigation into suspected espionage, state prosecutors said.
At the request of the special prosecutor’s office for the criminal offense of espionage, searches were conducted at several locations in Podgorica, a spokesman for the special prosecutor, Vukas Radonjic, told RFE/RL on September 29.
Individuals are suspected of "creating a criminal organization and espionage," Radonjic said, adding that there were no arrests.
Local media reported that police detained six Russian diplomats and up to 30 Russian citizens with temporary residency permits, alongside two Montenegrin citizens, on suspicion of working for Russian intelligence.
Outgoing Prime Minister Dritan Abazovic said the operation was undertaken alongside Montenegro's international partners in order to "preserve national interests."
Abazovic told reporters he hoped it would diminish "malign influences" in Montenegro.
Montenegro joined NATO in 2017 and adopted Western sanctions against the Kremlin following Russian President Vladimir Putin's invasion of Ukraine.
Russia has been cited as the source of a cyberattack that disabled state IT infrastructure beginning at the end of August and whose consequences are still being felt. Experts from the FBI assisted Montenegro in the investigation of the cyberattack.