By Tsvetelia Tsolova and Andrew Osborn
SOFIA (Reuters) - Russia's ambassador to Bulgaria said on Friday she would ask Moscow to close its embassy in the Balkan country after her appeal for Sofia to reverse what she called an unprecedented hostile step to expel 70 Russian diplomatic staff was ignored.
In a statement addressed to the Bulgarian people, the ambassador, Eleonora Mitrofanova, said the closure of the Russian embassy would inevitably lead to the closure of Bulgaria's embassy in Moscow too.
Bulgaria, an EU and NATO member state and once a close ally of Russia, has been roiled by diplomatic tensions after outgoing Prime Minister Kiril Petkov on Tuesday announced the expulsion of 70 Russian diplomatic staff on espionage concerns.
The move, which followed a sharp deterioration in ties over Russia's invasion of Ukraine, was the largest ever expulsion of Russian diplomats by Sofia and more than halved the size of Moscow's diplomatic footprint in Bulgaria.
Mitrofanova on Thursday told Sofia to reverse its decision by midday on Friday or face the prospect of Moscow ending its physical diplomatic presence in Bulgaria altogether.
Petkov earlier on Friday rejected her ultimatum.
"Unfortunately our appeal to Bulgaria's ministry of foreign affairs was ignored," Mitrofanova wrote in a statement.
"I intend to quickly put the question of the closure of Russia's embassy in Bulgaria before my country's leadership, which will inevitably mean the closure of the Bulgarian diplomatic mission in Moscow," she wrote.
In Moscow, Kremlin spokesperson Dmitry Peskov told Russia's Interfax news agency that the Russian foreign ministry would study the embassy closure idea and report to President Vladimir Putin if necessary.
Russia has accused Petkov of acting against Moscow on the orders of unnamed foreign forces, something he has denied.
'FREE BULGARIA' SAYS NO TO ULTIMATUM
Petkov called on the Russian government to withdraw the ultimatum, saying it was vital to keep diplomatic channels open despite the expulsions which he has said would still leave Russia with 43 diplomatic staff versus 12 for Bulgaria in Moscow.
"Our diplomatic relations should continue. We have history. Our peoples are friendly peoples. But no country should think that some diplomat could give ultimatums to independent and free Bulgaria," Petkov told reporters.
The EU earlier on Friday called Russia's ultimatum to Bulgaria "unjustified".
About 60 people gathered in front of the Russian embassy in Sofia on Friday to demonstrate against the government's decision to expel the Russian diplomatic staff.
Supporters of Petkov's decision plan a rally on Sunday at Sofia airport, when the 70 Russian diplomatic staff are due to leave the country.
Petkov has taken an unusually strong stance against Russia for a country that has traditional cultural, language and historical ties with Russia and was Moscow's most loyal satellite in Eastern Europe during the communist era.
He sacked his defence minister for refusing to call what Russia describes as a "special military operation" against Ukraine a "war".
Petkov has also backed EU sanctions against Moscow, refused to pay in roubles for Russian gas, welcomed Ukrainian refugees and agreed that Bulgaria will repair Ukrainian military hardware.
(Reporting by Tsvetelia Tsolova and Andrew Osborn; Additional reporting by Gabrielle Tétrault-Farber; Editing by Nick Macfie)