The Ukrainian army launched an attack with two Himars missiles against a Russian training camp near the village of Trudovskoye, Volnovakha district, Donetsk.
This was reported by the Russian-language BBC service.
At the time of the attack, which apparently occurred yesterday, the soldiers of the 36th Motorized Rifle Brigade of the Russian Guard were in formation on the training field.
According to estimates there would be around 60 victims among the Kremlin soldiers.
Photos and videos, which the BBC says it does not publish for ethical reasons, show dozens of deaths.
Ukraine did not comment on information about the Himars attack.
Meanwhile, the Ukrainian army has denied having lost control of the settlement of Krynki, its bridgehead on the occupied bank of the Dnipro river, in south-eastern Ukraine, the capture of which was announced yesterday by Russian President Vladimir Putin himself.
"The military and political leadership of the aggressor country announced the capture of the bridgehead on the left bank of the Dnipor River. We officially say that this information is false," the Southern Command of the Ukrainian forces wrote on social media.
The Ukrainian Air Force reported that it shot down a Russian Su-34 fighter-bomber last night: the commander of the Air Force, Mykola Oleschuk, made this known on Telegram, as reported by Ukrainska Pravda.
"Minus one, we continue to work. The crew of the Su-34 joins our column 'Eternal flight, brothers!'" the message reads.
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