Russian Deputy Foreign Minister Grigory Karasin has promised a "tough" response after Moldova ordered five of Moscow's diplomats in Chisinau to leave the country.

"The response will certainly follow, it will be quite tough," he said on May 29 after Chisinau declared the Russian envoys to be "personae non gratae" and gave them 72 hours to leave.

"It is a rude provocation, a blow to those forces in Moldova led by President Igor Dodon, who are really calling for normalizing and invigorating the bilateral relationship with Russia," Karasin told Russian news agencies in Moscow.

The diplomatic spat comes amid tensions between pro-Russia Dodon, who was elected late last year, and the West-leaning government, and follows allegations that a former Moldovan lawmaker passed state secrets to an attache of the Russian Embassy.

Former lawmaker Iurie Bolboceanu was arrested in March and charged with treason after a video was published of him meeting with the military attache of the Russian Embassy, Aleksandr Grudin.

The Moldovan Foreign Ministry did not give any reason for the expulsions on May 29, and did not name the diplomats it ordered to leave.

Dodon lashed out against the expulsions on Facebook on May 29.

"The government has taken an outrageous act toward the Russian Embassy," he said. "I am deeply outraged of this unfriendly step by the representatives of the Moldovan diplomatic corps and I categorically condemn it."

"This was done most likely on orders from the West," he said, adding that "this crude step will not be left without negative consequences."

Dodon has clashed repeatedly with the West-leaning government over ties with Russia and the European Union.

While the government has said it wants to join the EU and NATO, Dodon has opposed membership and said that he would like to cancel Moldova's EU Association Agreement.

With reporting by AFP, Reuters, Interfax, and TASS