Gazprom's refusal to supply Ukraine with gas for prepayment strips the Russian company its "take or pay" entitlement in 2018, CEO of NJSC Naftogaz Ukrainy Andriy Kobolev said.

"They haven't honored the obligations of the contract that the tribunal reviewed. This automatically means they will no longer be able to demand take or pay from us this year," Kobolev told Ukraine's Channel 5.

"We are not obliged to buy 4 billion cubic meters and this is not our fault. These actions by Gazprom, which contravene the contract, which contravene the tribunal's ruling, which contravene the spirit of relations between customer and supplier and which, I think, will cause Gazprom a lot of political problems in Europe," he said.