Russian company Gazprom has stopped gas supplies to Ukraine until Kiev pays for more energy, SIA informs.
Gazprom said that by 7am GMT on Wednesday Ukraine had received all the gas it had paid for and would not be sent more because the country had yet to pay in advance for future supplies.
Chief executive Alexei Miller warned that the stoppage posed a serious risk to the secure transit of gas to Europe via Ukraine, as well as to Ukrainian consumers.
Some 15% of the gas used in Europe travels through Ukraine.
In response to the announcement, Ukrainian Prime Minister Arseny Yatseniuk said his government would stop state energy firm Naftogaz from buying any more gas from Russia to reduce its energy dependence on Moscow.