"In the last 24 hours, Ukraine has illegally taken another 21 million cubic meters of Russian gas intended for delivery to Europe. As a result, since the beginning of year, just from Gazprom Ukraine has stolen more than 86 million cubic meters of gas," the company said in a statement.
"In addition, each day RosUkrEnergo does not receive 25 million cubic meters from the underground gas reserves of Ukraine," it added, calling on Ukraine to make up the missing volumes.
Gazprom also denied Ukraine's claim that no gas was flowing to Europe through its pipelines because the company was not pumping gas into them.
"Gazprom did not stop deliveries of gas to European consumers via Ukraine," the statement said.
Russian President Dmitry Medvedev joined the dispute via his spokeswoman on Wednesday.
"First of all it is necessary for Ukrainian side to stop illegally taking Russian gas intended for European consumers and passing through territory of Ukraine," Natalya Timakova said, adding that Ukraine had to "immediately open transit" to consumers in Europe.
Talks between Russia and Ukraine ended on New Year's Eve with no agreement on how to settle Kiev's gas debts or on a contract for 2009 deliveries.
Ukrainian President Viktor Yushchenko said on Wednesday in a letter to Medvedev and European Commission head Jose Manuel Barroso that Kiev was ready to restart negotiations any time. Oleh Dubyna, CEO of Ukraine's national energy company Naftogaz, is due in Moscow on Thursday for talks with Gazprom chief Alexei Miller.
The Russian president's spokeswoman reminded journalists on Wednesday that it was Ukraine who broke off talks a week ago.
"Discussions between Moscow and Kiev - Gazprom and Naftogaz - were interrupted on December 31 last year by the Ukrainian side," Natalya Timakova said. "Since then, representatives of Gazprom have repeatedly confirmed their readiness to continue negotiations without any preconditions."