The demands come after the Central Asian state of Turkmenistan, from which Russia gets a significant portion of its gas, said it was raising the price it charges Moscow.

"Our negotiations are under way. Our Russian partners have put forward new conditions on the price of gas," Ukrainian Energy Minister Yuri Boiko told reporters, without elaborating further.

Ukraine is the transit route for most of Russia's gas exports to European Union countries, which rely on Russia for about a quarter of their consumption. The gas pricing issue has led to tensions between Russia and Ukraine and last year prompted a brief cut-off in supplies, with knock-on disruption for several EU countries.

Although Russia holds the world's largest gas reserves, lack of development of those reserves means it has to supplement its supplies with imports from ex-Soviet Turkmenistan and other Central Asian states.

Russian press reports have said that European customers can expect a substantial increase next year in the prices they pay for gas from Russia.