Ukraine's national oil and gas company Naftogaz Ukrainy has paid Russia's Gazprom another $15 million, guaranteeing supplies of Russian gas until the middle of the month, Gazprom's official representative Sergei Kupriyanov told reporters.

He added that this estimate is fair "if it doesn't get cold and if requests don't grow."

"Based on Naftogaz's calculations [excluding Donbas], 63.3 million cubic meters [of gas] have now been paid for," Kupriyanov said, adding that the amount meant for March 6 totals 10 million cubic meters, he said.