Some ten million Ukrainians were left without electricity when dozens of Russian missiles hit power stations in the biggest aerial attack since the Russian invasion began in February.

On Wednesday fresh air raid alerts were sounding again across the country, raising concerns over new attacks, but the warnings were lifted in the capital Kyiv minutes after.

"After yesterday's rocket strikes, I was informed in the morning that most of the subscribers were reconnected," President Volodymyr Zelensky said on social media.

"Our engineers and rescuers worked all night in different regions," he said, vowing to "defeat all enemies".

The deputy head of Zelensky's office, Kyrylo Tymoshenko, specified that energy supplies have been fully restored in eight regions, mostly in western and central Ukraine.

In Kyiv, city military administration head, Sergiy Popko, said on Telegram that "thanks to the well-coordinated work of engineers and employees of all public utilities ... the power supply for critical infrastructure facilities has been restored."

The mayor of the western city of Lviv, Andriy Sadovyi, also reported that "power has been restored throughout almost the entire city".

"There are isolated reports of houses where there is no electricity yet. We are working on it," he said on social media.

On Tuesday, the Russian strikes also triggered automatic shutdowns of several reactors at two nuclear power plants as Moscow and Kyiv have traded blame for attacks near several nuclear plants in Ukraine.