Petro Andriushchenko, an advisor to the exiled mayor of Mariupol, said he obtained a document indicating that 101 Ukrainian children were registered at morgues in Russian-occupied Mariupol, Donetsk Oblast, in 2022.
A total of 133 children were registed across Donetsk Oblast as a whole.
The identities of only 87 of the dead children were identified, Andriushchenko said.
"They passed through three morgues — Mariupol, Mangush, Novoazovsk. A list of horror and death. It's hard to watch," Andriushchenko wrote on Telegram.
He noted that there are likely more children killed by Russia in occupied Donetsk Oblast, and that the information indicated in the document is only what Russian proxies in the region had access to.
According to the official, explosive injury, burns, and shrapnel wounds are among the listed causes of death.
"Whole families are here: Three children born in 2005, 2021, and 2015. Even a baby is less than a year old," Andriushchenko wrote on Telegram.
"What's next? Checking our data and a large investigation that will reveal where and when Russian bombs killed Ukrainian children. At least 101 of them have been identified and recognized by (Russian) occupiers," he added.
The Prosecutor General's Office reported on Aug. 19 that 502 Ukrainian children have been officially reported killed since the start of Russia's full-scale invasion last year.
More than 1,100 children have also sustained injuries of varying degrees of severity.
However, the actual numbers regarding child casualties may be much higher since they do not fully account for territories still under Russian occupation, recently liberated by Ukrainian forces, or experiencing heavy fighting, the Prosecutor General's Office added.