The workers were travelling home after finishing their underground shift when the attack occurred in Ternivka, Dnipropetrovsk region.
The CEO of energy company DTEK, which runs the mine, said "this was an unprovoked terrorist attack on a purely civilian target, for which there can be no justification."
Ukraine's President Volodymyr Zelensky offered his "condolences to all the families and loved ones".
"Today’s Russian drone strike on an ordinary bus carrying miners in the Dnipro region is a telling crime that yet again shows that Russia bears responsibility for the escalation. Evil must be stopped," he added.
The attack took place hours after Zelensky announced renewed peace talks.
Russian drones also targeted power infrastructure in the cities of Nikopol and Marhanets on Sunday, the president said.
Railway facilities in the Dnipropetrovsk and Sumy regions were hit as well.
In Kyiv, around 500 residential buildings remain without heating despite ongoing repairs, according to Zelensky.
Temperatures in the capital are expected to fall below minus 20°C overnight.
(ał)
Source: IAR, PAP