Russia says it has re-started pumping gas supplies for Europe through Ukraine but the EU says little or nothing is getting through.
Russia's state-owned gas monopoly Gazprom has accused Ukraine of syphoning off supplies destined for Europe for its own use but Ukraine is blaming a lack of co-ordination for hampering the flow.
Russia says it turned on the taps to re-start gas supplies to Europe through Ukraine on Tuesday morning.
Within hours the European Union said its monitors were warning that barely a trickle, if that, was coming through to third countries.
SOUNDBITE: Pia Ahrenkilde Hansen, European Commission spokesperson, saying (English):
"We are not at this stage jumping to conclusions as to why this is the case but this situation is obviously very serious and needs to improve rapidly."
Russia's state gas monopoly Gazprom is accusing Ukraine of blocking the flow of gas to Europe.
SOUNDBITE: Alexei Miller, Gazprom CEO, saying (Russian):
"Gas has reached Ukraine but not even a cubic metre of gas entered the Ukranian gas transit system. Gas flowed from our tap to the tap on the Ukranian side and the Ukranian side did not give us any clear explanation why gas can not enter the gas transit system"
Ukraine's state energy firm Neftogaz says the pipeline route Gazprom asked for could not be provided without cutting off supplies to parts of its own territory.
SOUNDBITE: Oleg Dubina, head of Neftogaz, saying (Russian):
"Unfortunately Gazprom's request to pump 76 million cubic metres of gas through the Sudzha compressor station and redirect it is impossible to implement with Ukraine's gas transit grid. The grid's been working as a single independent unit after Russia cut off supplies to Europe. If we start gas transit only in that direction as Gazprom requested we will leave Odessa, Donetsk, Lugansk and Donetsk region without gas. That's why I think Gazprom's request is aimed not to restore gas transit to Europe but to further aggravate the gas row."
Moscow and Kiev have been locked in a row over fees which has left European countries struggling for gas in freezing winter temperatures.
Russia is still refusing to supply gas to Ukraine and there is no sign of any thaw in relations any time soon.