Ukraine illegally siphoned off up to 40 million cubic meters of Russian natural gas for Europe over several days this month, Russian gas export monopoly Gazprom CEO Alexei Miller said on Wednesday, according to RIA Novosti.

Ukrainian Energy Minister Yuriy Boyko said this January that Ukraine was seeking to cut Russian gas imports to 27 billion cu m from 52 bcm. Gazprom reacted then by saying the current contract did not stipulate unilateral changes in gas purchase volumes.

"Ukraine kept up to 40 million cu m of gas for several days [in February]. This causes financial and reputational damage to Gazprom," Miller told President Dmitry Medvedev.

Several European countries said in early February they had faced shortfalls in Russian natural gas supplies, as a severe cold spell hit Europe, with temperatures plunging to below 30 degrees Celsius. Italy resorted to crisis measures to reduce the consumption of gas and maintain supplies to domestic customers.

Ukraine is probably the country worst affected by these extreme weather conditions. Russia’s southern neighbor is now importing natural gas, which is equal to an annual volume of 60 billion cubic meters, higher than the contracted volume of 52 bcm, which Ukraine denies.

Medvedev ordered Miller to take measures to solve the issue.

"Sort out [the issue] in terms of corporate and civil procedures," the president said.