Ukraine’s state-controlled gas transit company says Poland cut off reverse flows to Ukraine, alleging that a quarter of Russian gas imports to Poland went missing. Gazprom said it continues to supply the same amount of gas as previously.

Uktransgaz CEO Igor Prokopiv accused Russia of reducing supplies to "disrupt reverse deliveries" from Poland.

“At 2pm Poland stopped reverse gas flows to Ukraine, which had been in the range of 4 million cubic meters,” Prokopiv told journalists in Kiev on Wednesday. “Today Poland put in an order for 11 million cubic meters a day, and Russia confirmed orders for 7 million cubic meters. Those 4 million cubic meters are our reverse flows.”

Poland’s state-controlled gas company PGNIG said in a statement Wednesday that deliveries from Russia that traveled through Ukraine and Belarus had been reduced 20 percent on September 8 and 24 percent on September 9.

PGNiG said it was working to find out why volumes were down in the past two days.

In the meantime, Russia has denied that its state-run gas giant Gazprom has been limiting flows to Poland.

"Reports by news agencies on the reduction of volumes of gas supplies by Gazprom to Poland's PGNiG are incorrect,” Itar-Tass reported Gazprom spokesman Sergey Kupriyanov as saying. “The same volume of gas as in previous days – 23 million cubic meters a day – is being supplied to Poland now."

Before Gazprom issued its statement, Uktransgaz’s Prokopiv blamed Russia for trying to “derail” the plan for Poland to supply Ukraine with “reverse” gas, while Ukraine refused to pay its debt to Gazprom and is currently cut off from Russian supplies, and accused Russia of limiting the supply of gas.

Poland established a reverse-flow gas scheme with Ukraine in April 2014, under which Kiev can receive 4 million cubic meters of gas per day.

In August, Russia’s energy minister, Aleksandr Novak, warned that in the upcoming winter Ukraine may begin siphoning off Russian supplies intended for Europe if it fails to build up its reserves. He said that Ukraine had stockpiled up to 16 billion cubic meters of gas, but needed to pump as much as 10 billion more into storage.

Ukraine is seeking reverse-flow gas as it can no longer import gas from Russia, which halted non pre-payment gas deliveries in June over debt and pricing disputes. Gazprom says that Kiev’s Naftogaz has accumulated more than $5 billion in unpaid gas bills and also says it will not offer Ukraine a lower gas price than $385 per 1,000 cubic meters, a price Kiev is still fighting to reduce.

EU Energy Commissioner Guenther Oettinger said Sept. 3 that the bloc was preparing a "Plan B" to protect gas supplies in the worst-case scenario on energy security.

The plan would bar the EU from “re-selling” any gas to keep enough supplies to heat the continent through the winter months.

Ukrainian natural gas consumption is estimated at about 50 billion cubic meters per year, while the country’s own production is about 20 billion cubic meters.