Ukrainian investigators have begun work on the case of Mykola Karpiuk and Stanislav Klykh.
Russia's War Against Ukraine
Ukraine Today: Ukraine begins work to help two men held in Chechnya on accusations of killing Russian soldiers
Russian military troops take part in a military drill on Sernovodsky polygon close to the Chechnya border, some 260 km from south Russian city of Stavropol, on March 19, 2015.n