Ukraine's Prosecutor General's Office announced this on the Telegram messaging app, Ukrinform reports.
A pre-trial investigation has been launched into the violation of the laws and customs of war (Part 2 of Article 438 of the Criminal Code of Ukraine).
According to the investigation, at around 14:00 on Wednesday, September 6, the Russian invaders targeted a market in the center of Kostiantynivka.
Due to the impact of enemy shells, a fire broke out in the kiosks.
"As of 16:00, 16 people were killed in the attack by the occupiers. A further 31 people were injured, and they are receiving emergency medical care," the Prosecutor General's Office said.
Ukrainian Prime Minister Denys Shmyhal said earlier that a child was among those killed in the enemy attack on Kostiantynivka.