Kyiv accused Russia of planning to destroy a hydroelectric dam in the southern Kherson region, where Ukrainian soldiers have been steadily advancing and Moscow-installed authorities have begun evacuations.
Ukrainian President Volodymyr Zelensky said Russian forces had mined the Kakhovka hydroelectric power plant with the intent of blowing it up, in what would amount to a "catastrophe on a grand scale".
Hundreds of thousands of people around the lower Dnipro River would be in danger of rapid flooding if the dam was destroyed, Zelensky warned in a speech on Thursday to European leaders.
He said cutting water supplies to the south could also impact the cooling systems of the Zaporizhzhia nuclear power plant, Europe's largest.
And the North Crimean canal, which provides a crucial water supply to Crimea -- occupied since 2014 by Russia -- could be destroyed.
Russia's goal is to halt the Ukrainian advance in the region and protect Russian troops, according to Zelensky's adviser, Mykhailo Podolyak.
Energy battlefield
Cities across Ukraine began curbing electricity consumption ahead of winter Thursday as authorities warned that heavy damage to the country's energy grid by Russian attacks would spark a new wave of refugees from the country.
"Russia's leadership has given the order to turn the energy system itself into a battlefield. The consequences of this are very dangerous, again for all of us in Europe," Zelensky said in an address to the EU council
Energy-saving measures were put in place across the country after Russian missile and drone strikes destroyed at least 30 percent of the country's power stations in a week, according to authorities.
Following blackouts in parts of Kyiv overnight, the city's mayor Vitali Klitschko urged businesses to limit screens and signage lights "as much as possible".
"Even small savings and a reduction in electricity consumption in every home will help stabilise the operation of the national energy system," he said.
Ukrainians responded defiantly.
"It's not going to change our attitude, maybe we will only hate them more," said Olga, a resident of Dnipro in central Ukraine who declined to give her last name.
"I would rather sit in the cold with no water and electricity than be in Russia," she said.
People were rushing to buy auxiliary power supplies like generators and batteries, according to Kyrylo, an electronics vendor.
Speaking of the coming winter, he said: "I think that there will be nothing that we cannot survive."
"There will be some kind of heating in any case, and the fact that it will be 16 (degrees Celsius, or 61 Fahrenheit) instead of 20 doesn't matter much. Just put on a thermal and socks," he said.
Agence-France Presse