A Russian militant, who had fought alongside the separatists in occupied Donetsk, surrendered to the Ukrainian forces on July 11.
The 30-year-old reportedly served in the Vostok battalion, Ukraine's border patrol reported.
The militant, who lived in the city, allegedly had a violent disagreement with the so-called local police. The tensions escalated and he used his weapons during the conflict, the message said.
After that, the man decided to flee Donetsk and surrender. He was dressed as a civilian when he arrived at the checkpoint in the government-held town of Mariinka, around 25 kilometers west of Donetsk.
Read also: Ukrainian intel: Russian regular officer killed by militants in Donbas
He showed passports of the Russian Federation and the self-proclaimed South Ossetia when he was interrogated.
After the preliminary procedures were done, the man was transported to the department of the National Police, which will investigate his case.