Under Monday's deal with the European Union and Ukraine, Gazprom on Tuesday resumed pumping gas into Ukraine for transit to Europe. However, the transit gas did not reach Europe.
"This can mean only one thing - the Russian gas that is currently in Ukraine's transit pipelines has been stolen," Sergei Kupriyanov said.
He said Gazprom has received today a request from Ukraine for at least 140 million cubic meters of gas to ensure transit. "That is what they said: to refill the transit pipeline."
Valentin Zemlyanskiy, a spokesman for Ukrainian energy company Naftogaz, warned on Monday that Ukraine would continue using Russian gas being transited to European countries for technical purposes. However, Gazprom said Ukraine should either use its own "technical" gas, or buy it if the company lacks its own resources.
Kupriyanov said Gazprom is yet to establish the total volume tapped by Ukraine, saying that it had siphoned off 140 million cubic meters intended for the Balkan region alone.
A deputy CEO of Gazprom said Gazprom and its European customers would demand reimbursement from Ukraine for the halt in gas transit.
"We will use the entire legal arsenal. Not only will we demand payment of damages, but many consumer countries will too," Alexander Medvedev told journalists.
The move to resume gas supplies to Europe was made after Russia, Ukraine and the EU signed a deal on Monday allowing the presence of international monitors at Ukrainian and Russian gas transportation facilities to oversee gas transit.
Russia halted gas supplies to Europe on January 7, accusing Ukraine of tapping transit gas, which Ukraine denied.
Moscow cut off gas deliveries to Ukraine on January 1 after the parties failed to agree a settlement on Kiev's debt for supplies in 2008 and a price for a 2009 contract.