BRUSSELS, July 2 (RIA Novosti) - An EU expert group on gas advised EU members on Thursday to fill gas storage facilities to mitigate any potential gas cuts amid uncertainties in Ukraine, the European Commission said in a statement.

"In the light of the uncertain gas storage situation in Ukraine, the Commission in particular recommended the member states to be better prepared for the coming winter period and to fill their gas storages from all possible available sources," the statement reads.

Kiev is so far paying in full for Russian gas supplies. However, Moscow has voiced concerns on many occasions over Ukraine's ability to pay for gas, especially its ability to purchase gas from Russia to fill in its underground storage facilities and ensure uninterrupted transit to Europe.

Ukraine currently needs $4.2 billion to fill in its underground storage facilities. Russia has refused to be the sole creditor of Ukraine while European Commission President Jose Manuel Barroso said in early June it would be difficult for the European Union to help Ukraine keep up with its payments.

Russia, which supplies around one fifth of Europe's gas, briefly shut down supplies via Ukraine's pipeline system at the start of the year during a dispute with Kiev over unpaid debt.

The conflict was resolved in January, when Russian Prime Minister Vladimir Putin and his Ukrainian counterpart, Yulia Tymoshenko, agreed deals on deliveries to and gas transit through Ukraine for 2009.

Ukraine transits around 80% of Russia's Europe-bound gas.