Soldiers from the 98th airborne division based in central Russia were captured near the Ukrainian village of Dzerkalne, about 50 kilometres southeast of the rebel hub Donetsk, Ukraine's security service (UBS) said in a statement yesterday.
"Investigators opened a criminal probe into illegal border crossing by Russian armed citizens," it added.
The news comes just hours before Ukrainian President Petro Poroshenko is due to meet Russian leader Vladimir Putin for the first time in months alongside top EU officials in Minsk today.
"Today Ukrainian armed forces captured many Russian soldiers," Geletey wrote on his Facebook page.
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"Officially they are at exercises in various corners of Russia. In reality, they are participating in military aggression against Ukraine" and their families know nothing about their true fate, he said.
"I am addressing the relatives of Russian servicemen: find out immediately where your loved ones are. Take them out of Ukraine, where they are being forced to die," he added.
Kiev has long accused Moscow of stoking the separatist insurgency raging in its east but this is the first time Ukrainian authorities have claimed to take soldiers from Russia's regular army captive.
Earlier yesterday, Ukrainian military spokesman Andriy Lysenko said troops had halted a column of tanks and armoured personal carriers flying rebel flags from Russia heading towards the government-held port city of Mariupol.
But Russian Foreign Minister Sergei Lavrov dismissed the claims, saying "there has been more than enough disinformation about our invasion. No doubt some foreign newspaper will print that 'news' tomorrow".
Over 2,200 people have died and 400,000 fled their homes since April in fighting that has left residents in some besieged rebel-held cities without water or power for weeks.