Ukraine’s capital region was struck by Iranian-made kamikaze drones early Thursday, officials said, sending rescue workers rushing to the scene as residents awoke to air raid sirens for the fourth consecutive morning following Russia’s major assault across the country earlier this week.

Kyiv regional governor Oleksiy Kuleba said the strike occurred in the area around the capital. It wasn’t yet clear if there were any casualties.

Deputy head of the presidential office Kyrylo Tymoshenko said on Telegram that “critical infrastructure facilities” in the area were hit, without offering any details on which ones.

In the southern city of Mykolaiv, overnight shelling destroyed a five-story apartment building as fighting continued along Ukraine’s southern front.

Mykolaiv regional governor Vitali Kim said that an 11-year-old boy was rescued from under the rubble, where he had spent six hours, and rescuers on Thursday morning were searching for seven more people, Kim said.

He said that the building was hit by an S-300 missile which is ordinarily used for targeting military aircraft, but Russians have apparently been increasingly using them for unprecise ground strikes.

Early morning attacks on Ukraine’s southern front have become a daily occurrence in Russia’s war as Kyiv’s forces push a counteroffensive aimed at recapturing territory occupied by Moscow.