Russian President Vladimir Putin has warned that Moscow will cut gas supplies to Ukraine if it fails to pay in advance for future deliveries.
Putin said on Wednesday that Ukraine's latest payment would be good only for another three to four days, warning that Russia will have to turn off the tap if Ukraine does not remit payment quickly.
Putin did not announce a deadline, but warned that a cutoff may disrupt supplies to Europe.
Last week, Russia accused Ukraine of cutting gas supplies to areas in the east controlled by Russia-backed rebels. Putin said on Wednesday that what he called Ukraine's decision to halt gas supplies to the eastern regions, home to 4.5 million people, "smacks of genocide".
"There is hunger there, the OSCE talks about a humanitarian catastrophe, so it's only left to turn off gas taps," Putin said. "It looks like some Ukrainian leaders have no idea about humanitarian issues, about humanity."
Russian and Ukrainian gas officials may meet in Brussels later this week to discuss the situation.
Following a bruising dispute over prices and debt that raised fears of supply disruptions in Europe, Russia and Ukraine signed a deal in October requiring Kiev to pay in advance for gas shipments.
Russia then started pumping gas directly to the east, saying they should be counted as part of the overall volume of its gas exports. Ukraine protested that it cannot control gas distribution in areas outside its control.
Source: Associated Press