Rescuers in Ukraine are continuing their search for survivors in the wreckage of a big shopping centre hit by a Russian drone strike on Friday.

Sixteen people were killed and 130 injured when two drones hit the busy centre in Kryvyi Rih in quick succession in what is known as a double-tap strike. Four people are still missing. The search and rescue operation could last for another two days.

President Volodymyr Zelensky condemned the "cynical and despicable" attack in which the second drone targeted emergency workers.

The sides exchanged more fire overnight, with Ukrainian attacks said to have killed at least four people in Russia, including two children, and two people reported dead by Kyiv as a result of Russian strikes.

The death toll from Friday's attack reached 16 after another body was retrieved from the rubble overnight, said Dnipropetrovsk regional head Oleksandr Hanzha.

"We're doing everything possible to speed up... the search and rescue operation," he told Ukrainian TV on Saturday morning.

He added that the work could continue for another two days because of the sheer scale of devastation and constant threats of more Russian attacks.

Rescue teams from seven other Ukrainian regions were urgently deployed on Friday evening to help search for survivors.