Gazprom turned off gas supplies to Kiev last month after Ukraine failed to meet a deadline to pay off some of its gas debts. Europe receives around a third of its gas needs from Russia.
Meanwhile, a senior Russian official said he expected Ukraine to start "stealing" natural gas from pipelines carrying deliveries to the rest of Europe when its own supplies run low in the autumn, Interfax news agency reported.
"We know from experience that when autumn and winter come, and Ukraine is short of gas, they (Kiev) will, sorry for putting it this way, steal it," Sergei Ivanov, the Kremlin's chief of staff, was quoted as saying during a visit to China.