Kyiv residents should be prepared to leave the city if there is a total loss of power, its mayor has said.
In recent weeks millions of Ukrainians have intermittently been left without electricity and water, as Russian air strikes target vital infrastructure.
Rolling power cuts are also in place to avoid overloads and to allow for repairs.
Some 40% of Ukraine’s energy system has been damaged or destroyed by Russian attacks on power plants and lines.
Another city official has warned that, in the case of a total blackout, water supply and sewage would also stop working.
The Geneva Conventions, which outline humanitarian standards for treatment in war, state that attacks should not be carried out against “civilian objects”.
Speaking on Ukrainian television, Mayor Vitaly Klitschko branded Russia’s targeting of infrastructure as “terrorism” and “genocide”.
Russian President Vladimir Putin “doesn’t need us Ukrainians. He needs territory, he needs Ukraine without us”, the former heavyweight boxer said.
“That’s why everything that is happening now [strikes on infrastructure] is genocide. His task is for us to die, to freeze, or to make us flee our land so that he can have it.”
In winter in Kyiv, the average temperature is below freezing and drops even further at night.
Mr Klitschko said that while authorities are doing “everything” to keep the lights on and water flowing, he was ensuring preparations were in place for different scenarios.
Kyiv’s three million residents should make arrangements to stay with friends or relatives who live in the suburbs who still have water and power, so that they have a plan in the “worst case” scenario if the supply to Kyiv is lost, the 51 year old said.
He added that the authorities were stocking up on fuel, food and water, and residents should do the same. At least 1,000 heating shelters are being set up across the city where people will be able to get warm in an emergency.