A military spokesman says Ukrainian troops have arrested two Russian servicemen in Ukraine's separatist eastern territories.
Ukraine and NATO accuse Moscow of supporting pro-Russian separatists with troops and military supplies, a charge the Kremlin has repeatedly denied.
Spokesman Andriy Lysenko told a news briefing on May 17, that "two Russian servicemen are under arrest -- our investigators are working with them," without elaborating.
The Ukrainian Aidar volunteer battalion has claimed it captured the two Russian troops close to the town of Shchastya, which is controlled by government forces around 15 kilometers away from the rebel stronghold of Luhansk.
The battalion said on Facebook that the men captured were from Russian military intelligence, or GRU.
Lysenko said three Ukrainian servicemen were killed and 17 wounded in the past 24 hours.
Two of the soldiers died in a mortar attack near the town of Svitlodarsk, northeast of separatist-controlled Donetsk.
While violence has lessened significantly since a shaky cease-fire came into force in February, both sides accuse the other of violations and casualties are reported almost daily.