Ukraine has charged Captain Yevgeny Yerofeyev and Sergeant Aleksander Aleksandrov with involvement in "terrorist activity" and promised to release them should they fully confess during a "public" trial.
Kiev is trying to use the men's detention to prove its longstanding belief that the Kremlin was covertly supporting the rebels with high-tech weapons and troops in order to unsettle Ukraine's pro-Western government.
Russia's defence ministry says the two were once members of the armed forces but had been demobilised by the time they crossed into the Ukrainian war zone nearly two months ago.
They further accuse Moscow generals of washing their hands of their case for political reasons.
