Gazprom raises gas prices for Ukraine by almost 50%.

The government of ousted president Viktor Yanukovych had negotiated a discounted price last year as he grappled with protests after he dropped an association agreement with the European Union.

It “follows from Ukraine’s non-performance of obligations to repay the debt for gas supplies in 2013 and the lack of 100 percent payment for the current supplies,” Gazprom Chief Executive Officer Alexey Miller said. “The gas discount can no longer be used.”
This comes as no surprise. In any case the Ukrainian government might be well advised to declare with Western help the Russian loans 'odious' and just not pay a dime. Some informations about the legal aspects, although it depends of course much on the Western political will and the take by the financial markets. The latter would likely go wild if this was done in a 'normal' situation, but I doubt that such a special case will have significant consequences.

The issue about Gazproms credit is of course more difficult from a legal point of view, as I understand it. Not paying them would make a great deal of sense but this has to be looked at in greater detail.