Volodymyr Zelensky made the appeal in a video address posted on social media, Polish state news agency PAP reported.
Ukraine recently recaptured Izyum from Russian forces as part of its successful counter-offensive in the northeastern Kharkiv region.
Ukraine's president said: “Today, all our services - investigators, prosecutors, experts - are working in the city of Izyum, Kharkiv region. Today, there are more than a hundred Ukrainian and international journalists in Izyum.”
'Another mass burial of killed people'
He stressed: “Today, the world should see what the Russian army left behind - another mass burial of killed people: children and adults, civilians and military. Tortured, shot, killed by shelling.”
Zelensky added: “Even whole families were buried there - mother, father, daughter. More than 400 graves. In a forest near Izyum.”
He said that “We still don't know the exact number of bodies there. The exhumation has just begun," as cited by the Ukrinform news agency.
Evidence of torture
Zelensky also stated that investigators searching through the mass burial site near Izyum have found evidence that some of the dead had been tortured, with some bodies having broken limbs and ropes around their necks, according to the Associated Press news agency.
Ukraine’s president said: “[T]he world must see it. The world must know that Russia leaves such traces of atrocities, traces of terror, everywhere in the occupied territory. You saw Bucha. You saw Mariupol. Now it's Izyum.”
'Russia must be recognised as state sponsor of terrorism'
"Russia must be recognised as a state sponsor of terrorism. Otherwise, its terror will not be stopped," he added.
“Action must be taken so that Bucha, Mariupol, and Izyum do not happen again,” Zelensky stressed.
He also said that "Russia leaves only death and suffering," vowing that those responsible for the deaths of the people buried in the graves near Izyum would face “justly dreadful retribution,” the PAP news agency reported.
450 graves near Izyum: presidential official
Earlier on Friday, the Ukrainian president’s adviser Mykhailo Podolyak announced that there were 450 graves at the mass burial site near Izyum.
Podolyak tweeted: “450 graves... Only one of the mass graves discovered near Izyum. For months a rampant terror, violence, torture and mass murders were in the occupied territories.”
The official added: “Anyone else wants to 'freeze the war' instead of sending tanks? We have no right to leave people alone with the Evil.”
Meanwhile, the United Nations High Commissioner for Refugees (UNHCR) agency said on Friday it would seek to send its officials to investigate the circumstances of the deaths of the people whose bodies were being exhumed near Izyum, the PAP news agency reported.
Friday was day 205 of the Russian invasion of Ukraine.
Source: PAP, ukrinform.net, apnews.com