According to the newspaper Ukrainska Pravda, which refers to rescue forces, the missing may still be trapped under the rubble.
Around 300 people are reported to be injured after the attack, which occurred when two Russian rockets managed to penetrate Ukraine's air defense on Tuesday afternoon.
On Wednesday, Russia claims that the attack was "successful" and that "all designated targets were hit". In a statement from the Defense Ministry in Moscow, the target is said to have been a Ukrainian military training center, writes AFP.
According to Ukrainian reports, the rockets hit a military school building and a nearby healthcare facility. It is unclear which of the victims were military personnel and which were civilians.
The destruction is extensive on site – according to Ukrainska Pravda, 800 tons of rubble have been cleared so far.
Ukraine does not usually report how many soldiers are killed, but as far as is known, this is one of the deadliest individual incidents since Russia launched the full-scale war in Ukraine in February 2022.