Visible satellite shows what appear to be three isolated smoke trails (heading south-southwest) from locations near Kiev, and a smaller one near the Belarus border. This could be the source of the noise heard in Belarus overnight, some sort of heavy artillery fire by one or both sides (in Ukraine though).
These don’t look like natural clouds and weather is otherwise clear and cold in northern Ukraine, similar appearance to summer forest fire plumes in otherwise clear weather.
What sat feed are you using? Just curious.