Residents of the Ukrainian capital Kyiv were urged to head to air raid shelters early on Friday as sirens wailed across the city, a day after Russia carried out the biggest aerial assault since it started the war in February.

Shortly after 2.00 a.m. Kyiv's city government issued an alert on its Telegram messaging app channel about the air raid sirens and called on residents to proceed to shelters.

Olekskiy Kuleba, governor of Kyiv region, said on Telegram that an "attack by drones" was under way.

20 km (12 miles) south of Kyiv heard several explosions and the sound of anti-aircraft fire.

Ukrainian President Volodymyr Zelenskiy, in a video address on Thursday night, said air commands in central, southern, eastern and western Ukraine repelled 54 Russian missiles and 11 drones on Thursday.

Zelenskiy acknowledged that most regions were suffering power outages. The areas where loss of power was "especially difficult" included the capital Kyiv, Odesa and Kherson in the south and surrounding regions, and the region around Lviv near the western border with Poland, Zelenskiy said.