Undermining Russia's logistics is one of the elements of preparation for the expected Ukrainian counteroffensive, a Ukrainian military spokeswoman said on Sunday, after a fire destroyed a large Russian fuel depot in Crimea.

While not directly admitting to striking the fuel storage facility in the Crimean port of Sevastopol, Ukraine's military command said that "a fire" destroyed 10 oil tanks with a capacity of about 40,000 tonnes.

The city's Moscow-installed governor blamed Ukraine and later said the fire had been put out before a disaster occurred.

On Monday, air defense systems were repelling missile attacks in the early hours in the Kyiv region, local authorities said, after air raid alerts were issued throughout all of Ukraine by emergency services.

Natalia Humeniuk, a spokesperson for Ukraine's southern command, said the fire has cause a great deal of "anxiety" in the Russian military.

"The fact that the enemy's logistics are undermined ... this work is preparatory for the broad, full-scale offensive, which everyone expects," Ukrainian media cited Humeniuk as telling national television on Sunday.

"Therefore, the enemy feels that his resources are undermined and begins to maneuver."

On Friday, Ukraine said it was wrapping up preparations for the counteroffensive against Russian forces, although officials gave no date for when that would happen.

Kyiv has said it hopes its planned counteroffensive will change the dynamics of the war that has raged since Russia invaded Ukraine 14 months ago.