“Ukraine has cut off the delivery of gas to the territories of the Luhansk and Donetsk People’s Republics. This was done barbarically, the valves on the main pipeline were removed and they cannot be turned on again,” the source was quoted as saying by the Luhansk Information Center.
The temperature in the area has been hovering at around minus 5 degrees Celsius (25 degrees Fahrenheit).
“The republics have enough gas supplies until this evening,” the source said.
Gas supplies to the breakaway republic were cut on Monday night, the source said, but militias were able at first to switch to other strings of the pipeline, before the gas valves were shut off completely on Wednesday.
"It is possible to do. All measures have been outlined, and we are waiting for the [final] decision," the source added.
Breakaway regions of Donetsk and Luhansk have been arguing about energy supplies with the Ukrainian government in Kiev since the armed conflict broke out last April.
Kiev has also attempted to cut electric power deliveries to the Crimean peninsula in the south, after it broke off from Ukraine and rejoined Russia in March 2014.
Last December, the Ukrainian state-run energy firm Ukrinterenergo signed a deal with Russian energy holding Inter RAO to supply Crimea with electricity. But DPR and LPR are still heavily dependent on Ukrainian electricity and gas supplies.
Power shortages last year were one of the reasons that led to a severe humanitarian crisis in these regions, prompting Russia to send aid convoys with power generators there.