Russian energy company Gazprom said Ukraine owes about $7 billion to cover take-or-pay sections of an agreement. The Ukrainian government said it has no plans to pay the charges and has sought to diversify its energy sector.
Contractual disputes between Russia and Ukraine over natural gas supplies have exposed vulnerabilities in the European energy sector. European consumers get about 20 percent of their natural gas from Russia, with a majority of that heading through Ukraine's gas transit system.
Gazprom Chief Executive Alexei Miller said Ukraine was committing fraud because it was purchasing natural gas from Hungary that was from Russian suppliers. The Ukrainian government said there was no violation of the law in the trading scheme, Russian news agency RT reports.
The Ukrainian government said it received 23.2 percent less natural gas from Russia in January and February than it did during the same time last year. Gas transits to European consumers through Ukraine fell 24.3 percent in the same period, RT reports.
Ukrainian Prime Minister Mykola Azarov was quoted by Interfax last month as saying some gas diversification strategies were robbing the country of a "major trump card."