The European Commission voiced concern on Tuesday after Russian monopoly Gazprom said it cut gas supplies to Ukraine by a further 25 percent in a dispute over prices, according to The Guardian.

Commission spokesman Michele Cercone told a news conference that Gazprom had informed the EU executive about the latest cut, which reduces supplies to half of their normal level, and had said it would not affect gas transit to the European Union.

"They reassured us already yesterday that gas supplies to the European Union will not be affected. The Commission is concerned about the apparent reductions and urges both parties to go ahead in negotiations and quickly find a definitive solution to this commercial issue," he said.