At least 51 people were killed and 219 were injured on September 3 in one of Russia's deadliest attacks in a single strike since its all-out invasion of Ukraine.
Ukrainian President Volodymyr Zelenskiy and the country's Defense Ministry said two missiles struck a building of the Military Communications Institute in a morning attack on the city of Poltava in central Ukraine.
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They said two missiles hit the facility just after an air-raid alert and people didn't have time to evacuate to a bomb shelter.
"One of the buildings of the Communications Institute was partially destroyed. People found themselves under the rubble. Many were saved," Zelenskiy said.
Poltava regional Governor Filip Pronin said on Ukrainian television that as many as 15 people may still be under the rubble, adding that search teams were continuing to work at the scene.
The Prosecutor-General's Office announced that it launched an investigation as it released the new death toll of 51 late on September 3.
"At the moment rescuers, an investigative and operational group, and other services are working on the site, and the demolition of the debris is ongoing. The number of victims is being clarified," the Prosecutor-General's Office said on Telegram.
Zelenskiy said earlier that he ordered a "full and prompt investigation" into what happened. He also said he was "grateful to everyone who, from the first minutes after being hit, helps people who save lives."
Zelenskiy and Pronin described the site as an "educational" facility, and the identities of the victims were not immediately disclosed.
The attack is believed to be the deadliest single strike since May 2022, when Zelenskiy said 87 soldiers were killed at a military training center in the northern Chernihiv region.
Ukraine's defense readiness came under scrutiny after the strike on Poltava, and some observers questioned why a large number of people were left vulnerable to a single attack.
"A crowd of people at this facility in this number is absolutely unacceptable," said Yuriy Butusov, a Ukrainian activist and journalist. "We have a large number of military installations where there are significant numbers of people. These people in many cases that I have observed spread out so as so that they cannot be targeted by a single blow at the same time," he told Current Time.
Vladyslav Seleznev, a Ukrainian military analyst and former spokesman for the General Staff of the Ukrainian military, said Ukraine can blame the Kremlin for the strike on Poltava, but there must also be a clear understanding of Kyiv's responsibility.
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Ukraine's Defenses Under Scrutiny After Russian Air Strike Kills Dozens At Military Site
"The conversation we need to have is first and foremost about responsibility of officials who did not do anything that could have saved lives lost today during the Russian [air] strike," Seleznev said. "Why do children in Kharkiv attend classes underground or in a metro while [people at] the training center in Poltava did not have such an option?"
He also said the strike shows that Ukraine lacks monitoring systems needed to detect reconnaissance drones.
"Russia is not even trying to hide the fact that they were guiding their Iskander [missiles] toward the training center using a reconnaissance drone. If we had a sufficient amount of such monitoring and eventually strike systems, this kind of tragedy could have been prevented," he said.
In addition, Ukraine must realize the danger faced by all regions close to the front line. "The enemy is using ballistic [missiles] and the time [between their launch and] strike amounts to mere minutes."
Zelenskiy again urged Ukraine's supporters to step up the supply of air-defense systems and long-range missiles that can "defend against Russian terror," he said. "Every day of delay, unfortunately, means more lives lost."
Interior Minister Ihor Klymenko said emergency responders had saved many people and pulled some from the rubble. He said the impact site was near a residential area and shock waves from the blasts knocked out windows and damaged the facades of high-rise buildings.
After dozens of people reportedly turned up to donate blood, a message distributed via local media urged Ukrainians to avoid queuing up at blood-donation centers.
Maryana Bezuhla, deputy head of the Ukrainian parliament's National Security, Defense, and Intelligence Committee, appeared to suggest some sort of gathering had been targeted.
Alluding to a deadly Russian attack on a group of Ukrainian soldiers in the southern Zaporizhzhya region in November, Bezuhla said the incident "did not teach [us] anything."
"We have the repetition and repetition of tragedies. Where is the limit?" she wrote on X.
The Ukrainian military confirmed the deaths of at least 19 soldiers from the 128th Mountain Assault Brigade and nine others in that attack.
The incident sparked fierce criticism when it emerged that the soldiers had been gathered for an award ceremony.
Russia did not immediately comment on the Poltava attack.