KIEV, June 16 - Russia cut off gas to Ukraine on Monday in a dispute over unpaid bills that could disrupt supplies to the rest of Europe.

Calling time on weeks of wrangling in talks over natural gas supplies, Russia said Kiev had missed a Monday morning deadline to repay $1.95 billion owed for previous purchases and announced Ukraine would now only get gas it has paid for in advance.

At the same time, Moscow insisted that Ukraine must let Russian gas flow across the country through international pipelines to Russia's clients in the European Union - noting a temptation for Kiev to tap into those supplies in transit.

Kiev and Moscow blamed each other for the failure to agree on the price of future gas deliveries and refused to abandon well established positions: Russia offering a discount and Ukraine rejecting that as a tool for political manipulation.

The talks are bound up with the worst crisis between Russia and Ukraine since the Soviet Union collapsed - a crisis that has brought Western sanctions on Moscow, the Russian annexation of Crimea and Cold War-style saber-rattling along the borders.

"Thanks to the unconstructive position of the Ukrainian government, today a prepayment system was introduced," Alexei Miller, the chief executive of Russian state exporter Gazprom, told Prime Minister Dmitry Medvedev during a meeting at a government residence at Gorki, outside Moscow.

He said Ukraine had "adopted a position that can only be called blackmail", adding: "They wanted an ultra-low price."

At a news conference, he said it would no longer be enough for Kiev to pay part of its debt for supply to resume. That would now happen only once Ukraine paid off all the almost $4.5 billion and paid up-front for a month's deliveries, he said.

Ukrainian Prime Minister Arseniy Yatseniuk accused Russia of deliberately blocking a deal to cause Kiev supply problems next winter, when temperatures plunge and heating needs increase.

"But it is not about gas. It is a general Russian plan to destroy Ukraine," Yatseniuk said. "It is yet another step against the Ukrainian state and against Ukrainian independence."

A source at Gazprom said supplies to Ukraine had been reduced as soon as the deadline passed and Ukrainian Energy Minister Yuri Prodan said the country was receiving no gas.
Ukraine has at least 12 billion cubic meters of gas in storage, enough to meet its and the EU's needs over the summer.

A long-term reduction of supply could hit EU consumers, which get about a third of their gas needs from Russia, around half of it through pipelines that cross Ukraine. Earlier price disputes led to "gas wars" in 2006 and 2009, and Russian accusations Ukraine stole gas destined for the rest of Europe.

Gazprom's Miller said Russia would provide Ukraine with the volumes necessary to cover EU demand, but implied that Kiev may take some of those supplies for their own use - a potential shortfall Moscow could not be expected to cover. (rt/ez)