Russian missiles pounded Kyiv on Friday, families cowered in shelters, and authorities told residents to prepare Molotov cocktails to defend Ukraine's capital from an assault that the mayor said had already begun with saboteurs in the city.

Moscow claimed to have captured the Hostomel airfield northwest of the capital, a vital staging post for a planned assault on Kyiv, which has been fought over since the first hours of the war.

This could not immediately be confirmed and the Ukrainian authorities reported heavy fighting there.

"The city has gone into a defensive phase. Shots and explosions...