The EU urgently needs to develop a common energy strategy to cope with its dependence on Russian energy supplies, Bulgaria’s caretaker Foreign Minister Daniel Mitov has said.

The crisis in Ukraine threatens the security of Russian gas supplies to Europe, making Bulgaria highly vulnerable to any disruption, Mitov said at a two-day informal meeting of EU foreign ministers that started in Milan on Friday.

Russian gas giant Gazprom provides 27% of Europe’s gas supply. Fifteen percent go via Ukraine, which has the world’s largest gas-transit system, and the rest through the Nord Stream pipeline under the Baltic Sea and the Yamal pipeline through Belarus and Poland.

Should there be a disruption in Russian gas exports via Ukraine, Bulgaria will be among the countries hardest hit as it relies almost entirely on those supplies to meet its gas needs.

Mounting concerns over the movement of Russian military units in eastern and southern Ukraine were voiced at the meeting, the Foreign Ministry in Sofia said in a statement.

The incursion of Russian armed forces into Ukrainian territory is yet another blatant violation of Ukraine’s territorial integrity and sovereignty as well as a violation of international law, the statement read.

Moscow has repeatedly denied its troops fight alongside pro-Russian rebels in Ukraine’s eastern regions against Kiev’s government forces.

While highlighting the urgent need for consent among EU members for a response to Russia’s unilateral actions in Ukraine, including the imposing of new sanctions against Moscow, the foreign ministers agreed that efforts to conduct a dialogue with Russia should continue, the statement said.

Speaking after the meeting in Milan, EU foreign policy chief Catherine Aston urged Moscow to withdraw its forces from Ukraine and stop the flow of arms, equipment and personnel into the country.

EU leaders are to meet in Brussels on Saturday to consider their response to the crisis.