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KYIV, Ukraine — A man who appeared to be shot dead by Russian-speakers in a short video was tentatively identified Tuesday as a missing Ukrainian soldier while the footage circulated widely on Ukrainian social media and caused an uproar.

The country’s chief prosecutor announced a criminal investigation into the killing, and human rights chief Dmytro Lubinets argued that it was a violation of the Geneva Conventions.

Senior Ukrainian officials alleged, without providing further evidence, that the man was an unarmed prisoner of war killed by Russian soldiers. In the video, the man did not appear to be armed.

The 30th Mechanized Brigade on its Facebook page named the man as Tymofii Shadura. The identification is based on preliminary information and is not final, it said.

Shadura has been missing for just over a month, since disappearing during bitter fighting in the Bakhmut area of eastern Ukraine, the post said. The city has been a combat hot spot as the war extends into its second year.

His identity is to be confirmed once the body is returned from a Russian-occupied area, the post added, though it did not say when that might happen.

The Ukrainian military’s general staff gave the same name for the dead soldier, saying it was “according to preliminary information.”

In the 12-second video, the man in combat fatigues is seen in a wooded area smoking a cigarette.

Someone off-camera is heard speaking in Russian. The man then says “Glory to Ukraine” and is hit by a volley of gunshots, falling into a hole in the ground, with an off-camera voice saying “Die,” followed by an expletive.

The Associated Press could not verify the video’s authenticity, any details about when it was recorded or anything about the people involved.

Questions sent by the AP to the Russian military about the clip did not immediately receive a reply.

The video circulated widely on social media in Ukraine and unleashed an outcry.

In his nightly video address Monday, Ukrainian President Volodymyr Zelenskyy said: “I want us all together, in unity, to respond to (the soldier’s) words: “Glory to the hero! Glory to heroes! Glory to Ukraine!” And we will find the killers.”

Moscow also has expressed suspicion about the treatment of Russian prisoners of war by Ukrainian forces.

Last November, Ukraine said it would open an investigation into video footage that circulated on Russian social media, which Moscow alleged shows Ukrainian soldiers killing Russian troops who may have been trying to surrender after one of the men seemingly refused to lay down his weapon and opened fire.

In other developments:

— Ukraine and Russia completed another exchange of captives. Ukrainian presidential aide Andriy Yermak reported that 130 Ukrainian soldiers returned from Russian captivity, most of them with severe injuries. Russia’s Defense Ministry said 90 Russian servicemen were returned from territory controlled by Kyiv. Since the beginning of the war, 1,993 people have been returned from captivity, according to Lubinets.

— U.N. Secretary-General Antonio Guterres was on his way to Ukraine for a meeting Wednesday in Kyiv with Zelenskyy. The two are due to discuss the extension of an agreement that allows Ukraine to export grain from its Black Sea ports and permits Russia to export food and fertilizers.

— Ukraine’s presidential office reported Tuesday that at least one civilian was killed and 11 more were wounded in Ukraine over the previous 24 hours. Fierce battles continued in the region for the key city of Bakhmut, where fewer than 4,000 civilians remain from a prewar population of 70,000, according to Ukraine’s Deputy Prime Minister Iryna Vereshchuk.

— A parliamentary delegation from Hungary said Tuesday during a visit to Denmark that it supports Sweden’s NATO membership. Some Hungarian lawmakers had balked at supporting the NATO membership applications by Sweden and Finland, due to what they called “blatant lies” from Stockholm and Helsinki on the state of Hungary’s democracy.