Russian forces have fired more than 1,000 rockets and missiles at Ukraine's power grid, which is still working despite taking major damage, Interfax Ukraine news agency cited a senior official as saying on Wednesday.
Volodymyr Kudrytsky, chief executive of the Ukrenergo grid operator, also told a meeting arranged by the European Bank for Reconstruction and Development (EBRD) that his officials were scouring the world for the complex equipment needed for repairs.
Eight recent waves of Russian air strikes on critical infrastructure have seriously damaged the grid and led to emergency and planned outages across the country.
"These attacks represent the biggest blow to a power grid that humanity has ever seen. More than 1,000 shells and rockets were fired at electrical facilities and lines, including substations," Interfax Ukraine cited Kudrytsky as saying.
Ukraine now has a serious shortage of generating capacity, even though consumption is down between 25% and 30% compared to the pre-war period.
"The system is still working, it is integrated, not broken or disconnected," Kudrytsky said.
President Volodymyr Zelensky later said Ukraine was increasing the electricity supply every day but noted problems in Kyiv and several other regions.
"We should not forget ... that it is impossible to restore 100% of the energy system, as it was before the beginning of the Russian energy terror," he said in an evening video address.
"Time is needed. That is why scheduled blackouts continue in most of the cities and districts," he continued.
Ukrenergo said last week it had secured 300 million euros($315 million) in EBRD loans to restore power infrastructure damaged in the attacks and improve financial stability.