The main electricity and heat supplier in the Ukrainian capital said on Thursday it had started using oil to compensate for falling gas supplies, and residents reported a drop in temperature in their apartments.

It was not immediately clear whether gas deliveries fell because of a dispute with Russia, which has cut all supplies to Ukraine, or a longstanding local row over unpaid bills.

Some residents said temperatures in their apartments had fallen noticeably. The temperature in Kiev was about minus 8 degrees Celsius on Thursday morning, warmer than the day before when temperatures fell to lower than minus 20.

Ukrainian towns and cities are heated by central utilities which pipe hot water into flats and houses.

"We are able to keep the water temperature at 64 to 68 degrees Celsius by using fuel oil, the reserves of which are intended for emergency situations," Kievenergo <KIEN.PFT> said in a statement.

Kievenergo said gas supplies started falling on Jan. 6 and that on Jan. 7 its facilities had received 225,000 cubic metres of gas. It did not give figures for previous days or how much it usually gets.