Vladamir Putin (File)Russian Prime Minister Vladimir Putin has questioned Ukraine's reliability in paying Moscow for supplies of Russian natural gas and raised the possibility of another cut off.

Mr. Putin said Thursday he is concerned by the turmoil surrounding Ukraine's state-run gas company, Naftohaz.

Agents of Ukraine's security services raided the headquarters of Naftohaz Wednesday as part of an investigation into the fate 11 billion cubic meters of gas owned by a firm, RosUkrEnergo, that had been an intermediary in supplying gas to Ukraine. Ukrainian security agents also showed up Thursday at the office of a Naftohaz subsidiary, Ukrtransgaz, but left after being refused entry.

Ukrainian security agents at Naftohaz headquarters, 05 Mar 2009Mr. Putin warned that Moscow would cut natural gas supplies to Ukraine if Naftohaz did not pay its outstanding debt to Russia by Saturday. Hours later, Naftohaz paid off the balance remaining from a $360 million bill for Russian gas delivered in February.

Russia cut its gas shipments to Ukraine in January in a price dispute, disrupting supplies to many European countries for about two weeks at the coldest time of the year.

Mr. Putin said a new cut-off in gas supplies would again affect consumers in Europe, which depends on Russia for most of its gas imports. About 80 percent of Russian gas delivered to Europe passes through Ukraine.

The Ukrainian security agents who raided the Naftohaz office Wednesday were searching for copies of a Ukranian-Russian deal that ended the January gas dispute.

The raid is seen as part of a power struggle between Ukrainian Prime Minister Yulia Tymoshenko, who approved the Naftohaz deal with Russia, and President Victor Yushchenko, who criticized it.

Ms. Tymoshenko's government controls Naftohaz, which agreed to pay Russia a higher price for gas supplies. Mr. Yushchenko, who controls the security service, said the deal was not in Ukraine's interests.

Some information for this report was provided by AFP, AP and Reuters.