Russia has condemned Moldova's decision to expel five of its diplomats, calling it a move against the country's pro-Russian president.
Russia's response will be "quite harsh", Russian Deputy Foreign Minister Grigory Karasin said.
Moldova's pro-EU government announced the expulsions on Monday, without giving a reason. It is one of Europe's poorest countries and gets EU funding.
Moldovan President Igor Dodon called the move "outrageous".
"This has most likely been done on orders from the West, maybe even from across the ocean, by those who are worried that a constructive and effective dialogue has finally been found between the presidency and the Kremlin," he said.
It was an "unfriendly step" against a "strategic partner", he wrote on Facebook. He was elected president in November, after pledging to restore close ties with Russia.
The Russian ambassador was told that the five diplomats - not yet named - must leave Moldova within 72 hours.
Mr Karasin called the move "a deliberate blow against the intensification of Chisinau-Moscow relations, including against President Dodon's positions".