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.