They were detained in three separate incidents.
The military said a member of a subversive reconnaissance unit was captured after he stepped on a mine near the front line in eastern Ukraine. His unit left him behind and returned to its rear position after the incident.
The unidentified combatant received numerous land mine wounds and is being treated at a military hospital at an undisclosed location.
The Security Service’s (SBU) counterintelligence unit the same day detained a grenadier from the Donetsk regional town of Horlivka.
He was apprehended in the Azov Sea coastal city of Mariupol. The unidentified suspect fought against Ukrainian forces for nearly two years but was discharged after being wounded in 2016.
Toward the end of 2019, the man made his way to government-controlled Mariupol in search of work, the SBU said in a statement.
The internal security unit of the National Police detained another suspect in Kyiv on January 27 who fought with Russia-backed separatists.
On the night of January 24-25, the alleged former commander of a reconnaissance unit shot at an off-duty police officer in the chest outside a café in Kyiv.
The suspect was a former member of OPLOT, a pro-Russian militant organization that Ukraine has deemed illegal.