UPDATE 2-Ukraine PM says "difficult" Russian bill settled

* Ukraine PM says gas payment was extremely difficult

* President says Naftogaz could face $7.8 bln in fines

* Gas deal underlines Ukrainian political infighting

(Adds Naftogaz confirmation of payment)

By Sabina Zawadzki

KIEV, Nov 6 (Reuters) - Ukraine has paid Russia for October gas supplies on time, despite European Union fears that bills would not be settled but the process had proved "extremely difficult", Prime Minister Yulia Tymoshenko said on Friday.

Tymoshenko said her rival President Viktor Yushchenko and the central bank had thrown obstacles in the way of the payment to Russian gas giant Gazprom, reflecting behind-the-scenes struggles ahead of a presidential election due in January.

Her comments in a three-paragraph statement reflect a similar charge made by Russian Prime Minister Vladimir Putin [ID:nLU635960], who in October warned Yushchenko risked provoking a fresh crisis over gas supplies.

"Today we paid Russia the next $500 million," a statement from Tymoshenko's office cited her as saying. "The Ukrainian prime minister noted that this was extremely difficult to carry out," the statement said and then quoted her as saying: