Sgt. Dimko Zhluktenko, a commander of a drone team, told Business Insider what it was like flying in the heavy fog that Russia used to its advantage.

Moscow said the overnight strike was in response to an alleged Ukrainian drone strike on a residence used by President Vladimir Putin, which the U.S. and others said did not happen.

Russia said Friday it has used the new Oreshnik ballistic missile along with other weapons in a massive strike on Ukraine. Ukrainian officials said four people were killed and at least 22 wounded in the capital overnight.

Russia fired a hypersonic Oreshnik missile at Ukraine in retaliation for an alleged attack on one of Putin's residences that the U.S. and Ukraine have denied.

Ukraine's commander in chief said December was the first month that its drones "neutralized" roughly as many Russians as were called up.

President Vladimir Putin's launch of an Oreshnik hypersonic missile appears aimed at intimidating Ukraine and sending a signal of Russian military might to Europe and the United States at a crucial juncture in talks to end the war.

Russia bombarded Ukraine with hundreds of drones and dozens of missiles in a large-scale overnight attack, officials said Friday, killing at least four people. For only the second time, it used a new ballistic missile that it says flies at 10 times the speed of sound and is unstoppable.