Zelenskyy provided the number hours after rescue workers found the body of a two-year-old girl who died in one of the latest Russian strikes.
The president said in a statement that, “Russian weapons and hatred, which continue to take and destroy the lives of Ukrainian children every day”, killed the hundreds who had perished since Russia’s full-scale invasion of Ukraine started on February 24, 2022.
“Many of them could have become famous scholars, artists, sports champions, contributing to Ukraine’s history,” he said.
Zelenskyy said it was impossible to establish the exact number of children who were casualties due to the ongoing hostilities and because some areas are under Russian occupation.
“We must hold out and win this war!” the Ukrainian president said. “All of Ukraine, all our people, all our children, must be free from the Russian terror.”
Rescuers found the two-year-old’s body early on Sunday while combing through the rubble of an apartment building in the suburbs of the central city of Dnipro.
The regional governor, Serhiy Lysak, said five children were among 22 people injured by Saturday’s attack, which damaged two residential buildings.
The Russians launched more strikes with drones and cruise missiles on Sunday, targeting multiple areas of the country, including the capital, Kyiv.
The Ukrainian air force said the country’s air defences downed three of the five Shahed self-exploding drones and four of the six cruise missiles fired.
Ukrainian air force spokesman Yurii Ihnat said two missiles struck a military air base in Kropyvnytskyi, a city in central Ukraine’s Kyrovohrad province. He did not report what damage they caused.
The Russian military said it has conducted a series of strikes in recent days on Ukrainian air defence batteries, air bases and troop depots.
The long-range strikes come as Ukraine prepares for a long-expected counteroffensive in which it hopes to reclaim more ground.
Belgorod Governor Vyacheslav Gladkov reported more Ukrainian shelling of the border town of Shebekino that sparked several fires on Sunday.
In Crimea, which Russia illegally annexed from Ukraine in 2014, regional leader Sergei Aksenov reported a Ukrainian drone attack on the city of Dzhankoi early on Sunday.
He claimed that five of the attacking drones were shot down and four others jammed and were forced to land, adding that there were no casualties.
Concerns over civilian safety were exacerbated after officials announced that nearly a quarter of the 4,800 air raid shelters they inspected were locked or unusable.
The acknowledgement on Saturday came after a 33-year-old woman in Kyiv reportedly died while waiting outside a shuttered shelter during a Russian missile barrage on Thursday.
Prosecutors in the capital said four people were detained as part of a criminal probe into the woman’s death as she and others waited to enter a locked shelter.
A security guard who allegedly failed to unlock the doors remained in custody. Three others, including a local official, were placed under house arrest.
Mayor of Kyiv Vitali Klitschko said on Saturday that city authorities received “more than a thousand” complaints regarding locked, dilapidated or insufficient air-raid shelters within a day of launching an online feedback service.