Kiev (AFP) - Russia's state-owned gas giant Gazprom warned Tuesday it could cut off gas deliveries to Ukraine within two days, upping the stakes in the crisis there -- and threatening supplies to the rest of Europe.

The Gazprom announcement came hours ahead of a Paris meeting of the foreign ministers of Russia, Ukraine, Germany and France.

Ukraine's national gas company, Naftogaz, has already said the Russian company was not supplying gas Ukraine has paid for.

Gazprom last week started providing direct gas deliveries to parts of Ukraine under the control of pro-Russia separatists fighting government forces, supplanting Naftogaz deliveries disrupted by pipeline damage.

"Ukraine has failed to make a new pre-payment for gas in time," Gazprom CEO Alexei Miller said in a statement on Tuesday.

That "will in two days lead to a complete termination of the Russian gas supplies to Ukraine, which creates serious risks for the gas transit to Europe," Miller said.

He added that it takes two days for Gazprom to receive money transferred from Naftogaz.

But the Ukrainian company issued a statement accusing Gazprom of failing to honour pre-paid gas deliveries on Sunday.

"Naftogaz ordered 114 million cubic meters in line with the 'Winter Package' supply conditions, but Gazprom delivered only 47 million cubic meters," it said.

Naftogaz complained this was a "violation" of a supply deal signed in October in Brussels between the Russian and Ukrainian energy ministers and the European Commission.

Gas supplies to Ukraine are vital not only to provide heating and energy during the freezing winter, but also because of Ukraine's key role as a transit point for Russian gas to Europe.

Russia supplies around a third of Europe's gas, around half of it flowing via Ukraine.

Many eastern EU states are totally dependent on Russian gas, while Greece, Germany and Italy depend on it significantly.