Kiev- Siphoning of Russian gas moving to Europe by Ukraine was not taking place, a European Union official said Tuesday.

"We do not have any information that Ukraine performed unsanctioned siphoning of (Russian natural gas earmarked for Europe) after December 31," said Andris Piebalgs, the European Union's Energy Commissioner, at a Kiev press conference.

Piebalgs' remarks came on the first day of a resumption of Russian natural gas shipments to Ukraine, cut off at the end of 2008 over a series of Russo-Ukrainian disputes, among them Russian allegations that Ukraine had stolen Russian gas in the past.

Gazprom Vice Chairman Aleksander Medvedev at a Moscow press conference called Ukrainian theft of Russian gas prior to 2009 "an established fact," and said his company reserved the right to sue Ukraine for compensation.

Ukrainian officials throughout Europe's recent gas crisis have said they stole no Russian gas.

Russia re-opened its gas taps into Ukraine's gas pipeline system early on Tuesday, after talks between the leaders of the Russian and Ukrainian governments in Moscow over the weekend.

Minor rises in gas export volumes had been detected at Ukraine's Slovakian and Hungarian borders by Tuesday afternoon, with a return of full pre-crisis flow volumes expected on Wednesday. (dpa)