Russia on Friday threatened to close its embassy in Bulgaria and shut down the EU country's mission in Moscow as tensions rage over Moscow's offensive in Ukraine and espionage concerns.

This week Bulgarian Prime Minister Kiril Petkov said his country would expel 70 Russian diplomatic staff, the biggest number ordered out in one-go from the Balkan nation.

Russia's ambassador to Bulgaria, Eleonora Mitrofanova, said on Friday she would petition the Russian government to shut down the mission in Sofia.

"Unfortunately, our appeal to the Bulgarian foreign ministry has been ignored," she said in a statement released by the embassy.

She said she "immediately" planned to ask the Russian leadership to close "the Russian embassy in Bulgaria, which will inevitably lead to the closure of the Bulgarian diplomatic mission in Moscow".

She added that responsibility for the "grave consequences of this step" will rest with Petkov's government.

Petkov said that the Russian diplomats had "worked against our interests."

Multiple European countries have expelled Russian diplomats following Moscow's military intervention in Ukraine on February 24, with Russia responding in kind.

Bulgaria expects Russia to temporarily close its consulate general in Ruse in northern Bulgaria, while Sofia will temporarily close its consulate in the Russian city of Yekaterinburg, it said.

Bulgaria already expelled 10 Russian diplomats in March over Moscow's offensive in Ukraine.

The EU and NATO member --  once a staunch ally of the Soviet Union under communism -- still has close cultural, historic and economic ties with Russia.

But a series of espionage scandals since 2019 has soured relations between the two countries and seen some 20 diplomats and a technical assistant expelled.