More than 70 Ukrainian troops were killed when Russian troops shelled a military base in the town of Okhtyrka, regional governor Dmytro Zhyvytskyy said on Facebook.
Okhtyrka is located between Kyiv and Kharkiv in Ukraine's northeastern Sumy region, which borders Russia.
Zhyvytskyy also posted photographs showing the charred shell of a four-story building and rescuers searching rubble.
Convoy of military vehicles longer than initially thought
A massive Russian military convoy consisting of hundreds of tanks, trucks, towed artillery pieces and support vehicles has been pictured slowly making its way toward Kyiv.
Satellite images provided by the US company Maxar Technologies show the convoy spanning a distance of about 40 miles (65 kilometers). The Ukrainian news agency UNIAN also reported the same length early on Tuesday.
The convoy, which is longer than previously thought, is inching slowly toward the outskirts of the Ukrainian capital.
Up until now, Ukrainian forces have managed to slow the Russian invasion, but it is unclear just how long they will be to fend off the Russian push for the capital.
UN confirms more than 100 civilian casualties
UN human rights chief Michelle Bachelet has confirmed the deaths of 102 civilians, including seven children, since the Russian invasion began on Thursday. Hundreds more had been injured, and the figures provided were likely to be undercounted.
Residents of Kyiv who have remained in the city have hunkered down in the subway stations.
