This photo taken on Septe 21, 2020, shows Russian Foreign Minister Sergei Lavrov attending a press conference in Moscow. (PHOTO / AFP)

MOSCOW - Moscow on Thursday expressed regret at Bulgaria’s decision to declare two Russian diplomats ‘persona non grata’ and promised details on retaliatory measures at a later date, the foreign ministry said in a statement.

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Bulgaria on Wednesday said it had expelled two Russian diplomats who prosecutors suspect were involved in spying, giving them 72 hours to leave the Balkan country, a move the Russian Embassy in Sofia described as “groundless”.