"Ukraine has reportedly started tapping Russian gas intended for European consumers," Sergei Kupriyanov said.
"The figures, the exact volume of gas Ukraine stole today will be available January 2," he added.
Kupriyanov said gas feeding had dropped in four out of the five gas-measuring plants on Ukraine's western border as of 4 p.m. Moscow time (1 p.m. GMT)
"We are witnessing gas supplies decline practically in all directions," he said. "This is the gas intended for exports that Ukraine is tapping. We will specify losses tomorrow."
He confirmed the receipt of the contracts from Ukraine, but said Ukraine had not signed them.
Ukraine's national natural gas company Naftogaz said Sunday it had sent Moscow a draft contract stipulating new market prices for Russian gas starting from Q2 2006, after accepting Gazprom's terms December 31.
"Naftogaz was only willing to agree to separate parameters for Q1 2006 indicated in the [new] contract," Kupriyanov said.
