Ukrainian state energy firm Naftogaz on Monday said it would make payment in full and on time for May`s imports of Russian gas, Reuters reported.

"We are accumulating the funds," Naftogaz`s press secretary, Valentyn Zemlyansky, told Reuters. He gave no details on the volume of imports or the sum to be paid.

Payment for Russian imports has been a focus of attention since the two sides clinched a supply deal in January to end a three-week suspension of supplies that left hundreds of thousands of European consumers without gas.

Under the terms of that deal, Ukraine is to complete payment for monthly imports by the seventh day of the following month. No disruption in the payment timetable has so far been recorded.

But Russian officials have questioned Naftogaz`s solvency. And the two neighbors have so far failed to reach agreement on financial conditions for supplying gas to be kept in underground storage facilities in Ukraine.

Russian gas monopoly Gazprom last month described the situation with Ukrainian payment for gas as "very, very difficult."