Ukrainian President Volodymyr Zelenskyy condemned the “utter inhumanity” of the attack, which he said hit a regular market, shops and a pharmacy. “The number of casualties could rise further,” he said on X, formerly Twitter.
Prime Minister Denys Shmyhal said a child was among the dead, and Interior Minister Ihor Klymenko initially said 16 people were killed and 28 people were injured. He added that a rescuer was among the victims.
In a Telegram post later, Klymenko revised those figures and said 17 people were killed and 32 were injured.
Video captures explosion
The fiery blast came from nowhere, and within seconds debris and dust were flying into the air in video shared by Zelenskyy on Wednesday and geolocated by NBC News.
Shoppers are milling around before the explosion. For a brief second, people freeze, then some of them start to run.
The video then cuts to burning cars and buildings, a bloody floor in a store, and debris and rubble strewn across the street.
Russia has repeatedly denied that it is targeting civilians in what it calls its “special military operation” in Ukraine. Russia's Defense Ministry did not immediately reply to a request for comment about the attack on Kostiantynivka.
The attack overshadowed a visit by Blinken, a gesture of support from Washington as Kyiv's three-month-old counteroffensive searches for a decisive breakthrough.
Blinken, the first top U.S. official to visit Kyiv since the counteroffensive began in early June, met with Ukrainian Foreign Minister Dmytro Kuleba.
“We want to make sure that Ukraine has what it needs, not only to succeed in the counteroffensive, but has what it needs for the long term, to make sure that it has a strong deterrent,” Blinken said at a news conference ahead of the meeting.
Kuleba said in an earlier Telegram post, alongside a picture of him and Blinken, that they paid their respects to "fallen heroes" at Kyiv's Berkovetske cemetery.
Kostiantynivka is close to the front lines in the east, where Ukrainian forces have also been battling to push Russian forces back in the Donetsk region around Bakhmut.