Videos circulating on social media appears to show the moment of the explosion – and its graphic aftermath.

“The Russian troops are terrorists who will not be forgiven and will not rest,” Ukraine Prime Minister Denys Shmyhal says.

“There will be a fair retribution for everything.”

President Volodymyr Zelensky says Russian artillery was responsible and said it demonstrated “the audacity of evil.”

“At this moment, the artillery of Russian terrorists has killed 16 people in the city of Kostiantynivka, Donetsk region,” he adds.

“A regular market. Shops. A pharmacy. People who did nothing wrong. Many wounded. Unfortunately, the number of casualties and the injured may rise.“