Kiev (AFP) - Ukraine vowed on Monday to present to the public two Russian soldiers it claimed to have captured while fighting Moscow-backed forces in the separatist east. The politically-charged declaration came as a tenuous February truce was broken by more violence that claimed the lives of at least four Ukrainian servicemen. Russia firmly denies any involvement in the Ukrainian conflict and accuses the pro-Western leadership in Kiev of waging a war of attrition against its own people in the industrial east of the ex-Soviet state. But it concedes that some "volunteers" and off-duty soldiers may have crossed Russia's southwestern border to support separatist militias fighting in Ukraine's Lugansk and Donetsk rustbelt. "For us, it is very important to present to the entire world Russian soldiers who supposedly do not exist on our land," Ukrainian military spokesman Vladyslav Seleznyov told AFP. "These are fighters from the 3rd non-divisional brigade of the special forces. They are based in (the Volga River city of) Togliatti," he said. Another Ukrainian defence spokesman told reporters that the wounded soldiers had been treated in hospital and were being flown to Kiev for their public appearance on Tuesday. Kiev's claim was dismissed by Russian President Vladimir Putin's spokesman Dmitry Peskov. Both the military and other Moscow authorities have repeatedly stressed that "there are no Russian soldiers in the Donbass," Peskov said, referring to eastern Ukraine. "But I otherwise cannot comment," Peskov told Moscow Echo radio. "In this case, this is something for the experts or our defence ministry to do -- to say how plausible this material is."