The missile struck a residential area near a children's playground and wounded more than 50 people, according to the head of the city's military administration.

Unverified videos on social media appeared to show bodies lying on a street, while another showed a plume of smoke rising into the evening sky.

"It was preliminarily a ballistic missile attack. As of now, 14 people have been killed, including six children," Zelensky said on Telegram.

The rescue operation was ongoing, he added.

Regional governor Sergiy Lysak said the number of reported casualties was "constantly increasing".

"There is only one reason why this continues -- Russia does not want a ceasefire and we see it. The whole world sees it," Zelensky said.

"And only the world's pressure on Russia, all efforts to strengthen Ukraine, our air defence, our forces -- only this will determine when the war will end."

The Ukrainian leader was born in Kryvyi Rig, which had a pre-war population of around 600,000 people.

US President Donald Trump's administration has been pushing for a speedy end to the more than three-year war, holding talks with both Russia and Ukraine.

Moscow has rejected a joint US-Ukrainian proposal for an unconditional and full ceasefire, while Ukraine has accused Russia of dragging out talks with no intention of halting its offensive.

- 'War crime' -

Kryvyi Rig, in Ukraine's central Dnipropetrovsk region, is about 60 kilometres (37 miles) from the front line but has regularly been targeted by Russian drones and missiles.

A previous Russian ballistic attack on the city on Wednesday killed at least four people and wounded more than a dozen others.

Oleksandr Vilkul, the head of the city's military administration, said the missile landed near a children's playground.

Five apartment buildings were damaged, interior minister Igor Klymenko said.

He said police had blocked off the area to maintain order.

"The police are documenting the consequences of Russia's war crime and accepting statements from the victims," he added.

Social media video from the scene showed a car in flames, while people could be heard shouting.

Andriy Kovalenko, a Ukrainian official tasked with countering disinformation, described the missile involved in the attack as an "Iskander".

The Iskander is a Russian ballistic missile system that can have a range of up to 500 kilometres (311 miles).

"This is a deliberate strike to kill a large number of people," Kovalenko said.