The death toll from Russian strikes on a hardware store in the eastern Ukrainian city of Kharkiv rose to 16 Sunday, the regional governor said, as rescuers searched the charred debris for bodies.

"Unfortunately, 16 have already been recorded dead," Oleg Synegubov, Kharkiv regional governor, said on Telegram, while 43 were wounded.

Russian strikes hit the Epitsentr superstore on Saturday, sparking a massive fire that makes the dead hard to identify.

Police said six of the dead had been identified, including a 12-year-old girl who was visiting the city, while several people were still listed as missing.

Police were asking relatives to give DNA samples to help identify bodies in the ruined store in the northeastern outskirts of the city.

Earlier, Synegubov said two of those killed worked in the hypermarket.

A video posted by police showed staff and shoppers in the store before an explosion erupted, followed by flying debris and darkness.

"It took 16 hellish hours to tame the flames" of the subsequent fire, Interior Minister Igor Klymenko said on Telegram.

'Everything was burning'

Still wearing her uniform, Lyubov, a cleaner at the store, recalled how she escaped the building as the fire broke out. 

"It happened all of a sudden. We didn't understand at first, everything went dark and everything started falling on our heads," she said. 

"It was good that my phone lit up, thanks to the flashlight I found where to go, but in front of us everything was burning already." 

Ukraine's President Volodymyr Zelensky condemned the daylight attack on an "obviously civilian" target.

"Only madmen like Putin are capable of killing and terrorizing people in such a vile way," he said, referring to Russian President Vladimir Putin, who ordered his troops into Ukraine in February 2022. 

Kharkiv, Ukraine's second-largest city, is just a few dozen kilometers from the border and regularly comes under attack from Russian missiles.

Russia's TASS state news agency cited a security source who said the hypermarket strike destroyed a "military store and command post" inside the shopping center.

Peace summit call

On Sunday, Zelensky urged US President Joe Biden and Chinese leader Xi Jinping to personally attend a planned peace summit in Switzerland in June, in a video message standing in front of a publishing house bombed in Kharkiv last week.

"I am appealing to the leaders of the world... to President Biden, the leader of the United States, and to President Xi, the leader of China... Please support the peace summit with your personal leadership and participation," Zelensky said.

The high-level conference on the Ukraine war is to be hosted in Lucerne on June 15-16 by the Swiss government at Ukraine's request.

Bern has said it has invited 160 delegations but that Russia will not attend. 

China has said it supports an international peace conference recognized by both Russia and Ukraine.

Missiles, drone strikes

Ukraine's air force said Russia had launched another 14 missiles and more than 30 attack drones on Ukraine overnight into Sunday.

It said it downed all but two of the missiles.

In the central Vinnytsia region, fragments from a downed drone wounded three people and damaged houses and blocks of flats, regional authorities said.

Sirens sounded in the Kharkiv region Sunday afternoon and a 72-year-old woman was killed in the village of Boguslavka while two were wounded, including a nine-year-old boy, Synegubov said.

The latest attacks came after Russia launched a ground offensive in the Kharkiv region on May 10. 

Ukraine said Friday that it had managed to halt Moscow's progress and was counterattacking. 

Russia on Sunday claimed the capture of the village of Berestove in the Kharkiv region, located on the eastern front line close to the Lugansk region.

In the eastern Donetsk region, the public prosecutor's office on Saturday reported three deaths in the towns of Siversk, Chasiv Yar and Krasnogorivka.