The accusation, after Russia cut supplies for the Ukrainian market on New Year's Day, prompted a denial from Ukraine, which said some "technical" gas was being used to maintain pressure in pipelines that run through its territory.

The row which blew up over unpaid gas bills and fines levied by Russia on Ukraine, has raised concern in European Union states that depend on Russian gas supplies, most of which flow through ex-Soviet Ukraine, said an AFP report.

In televised comments, a spokesman for Russian gas giant Gazprom, Sergei Kupriyanov, asserted: "The Ukrainian side openly admits it is stealing gas and has no shame about it."

He put the amount of gas he said had been illegally "syphoned" from pipelines crossing Ukrainian territory at 21 million cubic metres since yesterday.

He added that Ukraine was refusing to allow Russia to send the full amount of gas required for clients in Europe across Ukrainian territory on Saturday.

"Regarding the next 24 hours, the Ukrainian side did not agree to the transit volume required by us. We made a request for 303 million cubic metres but were refused this and permitted 296 million cubic metres," Kupriyanov said.

Separately, Russian Deputy Foreign Minister Alexander Grushko said: "We propose calling an emergency session of the European parliament in order to give the Russian side a chance to express its views" to the European Union directly.

Ukrainian state energy company Naftogaz denied Gazprom's accusation that it was stealing gas but said the situation concerning "technical gas" used to maintain pipeline pressure was unclear after the breakdown of talks on New Year's Eve.

"We are not stealing gas. We are removing gas for technical purposes, in order to ensure the transit of Russian exports" to Europe, Naftogaz spokesman Valentin Zemlyansky told AFP.

"Normally Russia should provide this 21 million (cubic metres) with the transit volume," he said, adding he had not received the corresponding documentation on technical gas from Russia.

"We're not going to use our own gas to ensure transit," he said.

As the row continued, the European Union urged the two sides to settle their differences, although European officials said their countries were not experiencing any supply problems.

"It is unacceptable for the EU and for the Czech Republic that a bilateral disagreement between two private companies should threaten respect of international agreements in a sector as important from the economic and strategic point of view," said Jiri Frantisek Potuznik, European affairs spokesman for the Czech Republic, current holder of the EU presidency.

A spokesman for EU Energy Commissioner Andris Piebalgs, Ferran Tarradellas, said supplies were being monitored closely but no disruption had been reported.

Kupriyanov said Gazprom had increased supplies through its other pipeline route to Europe, Belarus, which normally handles about 20% of Russia's gas shipments to European customers.

A Ukrainian delegation led by Energy Minister Yuri Prodan began touring European capitals to discuss the consequences of the dispute and provide reassurance.

"The main aim of the tour is to present the necessary explanations to EU member countries over the situation, to give guarantees on the transit through Ukrainian territory and consult European specialists," an aide to Ukrainian President Viktor Yushchenko said in a statement.

Gazprom's chief executive Alexei Miller has scotched hopes of a quick deal , saying Ukraine would have to pay a "European price" of $418 per 1000 cubic metres of gas in 2009, more than double what it paid last year.

Russia earlier offered Ukraine a price of $250 which Kiev turned down, arguing it should receive an increase in payments for gas transit.

The price of $179.5 that Ukraine paid last year is well under the amount paid by European countries for Russian gas.

Published: 02 January 2009 17:56 GMT  | Last updated: 02 January 2009 17:56 GMT