(BRUSSELS) - The European Commission said it was "strongly concerned" Wednesday after a natural gas payments row between Russia and Belarus left Lithuania with only half its normal supply.
"This afternoon, Lithuanian authorities have confirmed that gas supplied via the national Belarus gas pipeline system has been cut by around 50 percent," EU Energy Commissioner Guenther Oettinger said in a statement.
Such gas cuts "are not acceptable," he added.
Lithuania had earlier announced that its supplies were cut by 40 percent.
Oettinger earlier described the cut to Lithuania's supplies as an "attack" on the whole European Union.
Russia had cut gas supplies to Belarus by nearly two thirds on Wednesday morning, amid a payments dispute.
Belarus said later that it had paid its debt to Russian gas giant Gazprom in full and threatened to shut down the flow of Russian gas to Europe if the firm did not pay transit fees by Thursday.
Three EU countries can be potentially affected by the gas dispute: Lithuania, Poland and Germany.
In the case of Poland and Germany, Russian gas could be delivered via Ukraine, but this is not possible for Lithuania which relies upon Russian gas delivered via Belarus.
Latvia is expected to be able to deliver gas to Lithuania for a week, as an emergency measure.