EU sanctions against Russia will gradually hit Moscow's oil revenues, despite the fact that they do not directly target Russian oil and gas exports, European Commissioner for Energy Policy Kadri Simson said, Reuters reported.

The EU has imposed several packages of sanctions against Russia, including a ban on exports to Russia of certain refining technologies from Europe, which makes it difficult and expensive to modernize Russian refineries.

These technologies are developed in Europe, other vendors cannot easily place them all over the world, Simson said.

Oil and gas sales in Russia accounted for 36% of the country's total budget last year, well above initial forecasts as a result of skyrocketing prices.

Europe imports 90% of its gas, about 40% from Russia.

The EU says it will be able to deal with a partial supply disruption to Russia this winter thanks to increased imports of liquefied natural gas and relatively good storage levels. However, a complete or prolonged cessation of supplies from Russia will require emergency measures to reduce demand, such as plant closures, analysts say. All EU countries have contingency plans in place in the event of interruptions in gas supplies.