"At 2:30 a.m. Central European Time, the Ukrainian side switched off three main export gas pipelines to Western and Central Europe," A. Medvedev told reporters at a joint press conference with German Economy Minister Michael Glos, broadcast by Vesti-24 TV channel.

"As a result, irrespective of our desire to supply gas to European consumers, we have been deprived of a physical opportunity to supply gas to Europe at full volume," Gazprom's vice president said.

"We are using alternative supply opportunities through the Yamal-Europe pipeline and from our underground terminals," A. Medvedev said.

"Unfortunately, at present we are unable to compensate for the gas stolen by Ukraine because three main transit pipelines have been shut. This worries us most. Our opportunities to compensate for the stolen gas have been essentially reduced," he added.

In 2005-2006, "the following day after gas theft was registered, we began compensating for the stolen gas by increasing supplies through Belarus and Ukraine, while continuing to search for a solution at parallel talks," A. Medvedev said.

"Regrettably, there have been no talks during the past days simply because the Ukrainian delegation did not have the authority to conduct them. We think it necessary to speedily find a solution to avoid potential technical consequences of the current dispute," he said.

"The volume of supplies at least two hours ago was four times less than the normal level. Unfortunately, the Ukrainian side threatens with further cuts," A. Medvedev said.

The gas pipeline through Orlovka has been fully shut off with Ukrainian also threatening to switch off the pipeline through Berehovo, he added.

There is only one way out: agreements on gas supply, to replace the ones that have expired, must be signed and Ukraine must stick to its obligations as a transitor state, A. Medvedev said.