Ukraine's Security Service (SBU) reported the detention of a former militant fighting as part of the Moscow-led Sparta battalion in Donetsk Oblast.
The suspect allegedly joined Russian-controlled militants in 2015, fighting against the Ukrainian military in the country's east, but after being wounded, he returned to his hometown in Odesa Oblast.
"As part of an enemy group, he fired at defensive positions of Ukrainian troops, fought in the Donetsk airport area, served on checkpoints, and studied at 'sniper courses,'" the SBU wrote on March 6.
After going back to the Ukrainian-controlled territory, the suspect was hiding from justice and stayed in touch with his associates from the Moscow-backed militant group, according to the report.
SBU charged him with "terrorism" and placed him under arrest.
Russia invaded and partially occupied the Donbas, made up of Ukraine's eastern Donetsk and Luhansk oblasts, in 2014.
The Hague District Court qualified the Russian invasion of eastern Ukraine in 2014 as an "international armed conflict" and recognized that Russia had control over proxies in Donetsk Oblast since mid-May 2014.
