Snipers have been trained in occupied Donbas since 2016.
Russia's security forces use the territory of Ukraine as a testing ground for new sniper weapons.
The Ukrainian Defense Ministry's Main Intelligence Directorate says regular sniper units were formed as part of the 1st and 2nd Army Corps of the so-called "Donetsk and Luhansk People's Republics" in 2016, and they are trained by Russian instructors, according to RFE/RL's Ukrainian service.
According to the Defense Ministry, such units consist of about 450 snipers.
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Since 2016, snipers have been trained in occupied Donbas, he said.
"According to military intelligence, the sniper units underwent training in the occupied districts of Ukraine last December with the involvement of officers of the Russian armed forces as instructors, who came from Rostov region to conduct the training, individual classes, and monitor the results of the training of the 1st and 2nd Army Corps' sniper units," Skibitsky said.