Sirens are sounding in Kyiv and other densely populated cities, with officials describing the incoming barrage as the latest in a series of waves.
Ukrainian air force spokesman Yuriy Ihnat said some missiles have “already been launched”.
But officials are yet to report deaths or injuries.
Pictures and videos show Ukrainians crowded in local metro stations, and the country has reportedly shot some missiles down.
Another wave may follow bound for Kyiv, according to local sources.