The intense strikes with 17 drones sparked fires in 15 units of a five-storey apartment building and caused other damage in the city close to the Russian border, Kharkiv Mayor Ihor Terekhov said.
"There are direct hits on multi-storey buildings, private homes, playgrounds, enterprises and public transport," Terekhov said on the Telegram messaging app.
"Apartments are burning, roofs are destroyed, cars are burnt, windows are broken."
A Reuters witness saw emergency rescuers helping to carry people out of damaged buildings, administering care and firefighters battling blazes in the dark.
Nine of the injured, including a two-year-old girl and a 15-year-old boy, have been hospitalised, Oleh Sinehubov, the governor of the broader Kharkiv region, said on Telegram.
He added that the strikes hit also a city trolley bus depot and several residential buildings.
There was no immediate comment from Russia. Kharkiv, in Ukraine's northeast, withstood Russian full-scale advance in the early days of the war and has since been a frequent target of drone, missile, and guided aerial bomb assaults.
The attack followed Russia's two biggest assaults of the war on Ukraine this week, a part of intensified bombardments that Moscow said were retaliatory measures for Kyiv's recent attacks in Russia.
Both sides deny targeting civilians in the war that Russia launched on its smaller neighbour in February 2022. But thousands of civilians have died in the conflict, the vast majority of them Ukrainian.
"We are holding on. We are helping each other. And we will definitely survive," Terekhov said. "Kharkiv is Ukraine. And it cannot be broken."
The strike came hours after Russia and Ukraine have exchanged more prisoners of war, both sides say, without giving details of the numbers involved.
The exchange was agreed between the two sides at talks in Istanbul last week and an initial swap of prisoners under the age of 25 was conducted on Monday.
The group of Ukrainian prisoners consisted of seriously ill and severely injured soldiers, Ukrainian President Volodymyr Zelenskiy wrote on X.
Among them were members of the army, the National Guard, transport services and border guards, Zelenskiy said.
Earlier, the Kremlin said it had been ready for several days to start handing over the bodies of Ukrainian soldiers killed in the war but that Ukraine was still discussing the details.
The planned transfer of thousands of war dead was the other tangible result of the Istanbul talks, which resumed last month after a gap of more than three years but have made no progress towards a ceasefire.
Russia has said it is ready to hand over the bodies of more than 6000 Ukrainian soldiers and receive any bodies of Russian soldiers which Ukraine is able to return.
But Kremlin aide Vladimir Medinsky said on Saturday that the Russian side had shown up at the agreed exchange point with the bodies of 1212 Ukrainian dead soldiers only to find nobody from Ukraine to take them.
with DPA
