Ukrainian authorities have discovered a mass grave near a northeastern city previously held by Russian forces, President Volodymyr Zelensky announced Thursday night.

The grave was found near the city of Izium in the Kharkiv region.

“The necessary procedures have been initiated there. "More information - clear and verifiable information - will be available on Friday," Zelensky said in his televised speech tonight.

Ukrainian authorities have discovered a mass grave containing more than 440 bodies in a forest outside the eastern city of Issyam. The graves were discovered while scanning the site for hidden explosives using metal detectors.

Serhii Bolvinov, the chief police investigator in the Kharkiv region, said that a forensic investigation would be conducted on all of them and that some of them had been killed by shelling and airstrikes.

"Videos posted on social media by Russian soldiers indicate that there are more than 17 bodies in the grave. "We haven't counted them yet, but I think there are more than 25 or 30," said Oleg Kotenko, an official at the Ukrainian ministry tasked with restoring the occupied territories.

Zelenskyy invoked the names of other Ukrainian cities where authorities said retreating Russian troops left behind mass graves of civilians and evidence of possible war crimes.

Some of the people buried in the pit were shot. Others died from artillery fire, mines or airstrikes. Many of the bodies have not been identified yet, Bolvinov said.

Russian military bloggers said the attack was intended to flood areas downstream where Ukrainian forces made inroads as part of their counteroffensive.

The head of the local government on Thursday reported a new attack on the dam and said emergency crews were working to prevent more water from escaping.

The first attack so close to his roots angered Zelenskyy, who said the strikes had no military value.

"In fact, hitting hundreds of thousands of ordinary civilians is another reason why Russia will lose," he said.