They are laying down new tracks in Abhkazia – but it is Russia’s state-owned railway that is carrying out the work.
Moscow is helping the breakaway Georgian region finish a project to restore a vast stretch of line.
The railway will link Abkhazia to the Russian city of Sochi and strengthen ties between the Black Coast entity and its neighbour.
Abkazia’s minister for the economy said the region’s young government had little experience with such massive projects and welcomed the help from Russian Railways.
But Georgia has protested, reportedly claiming Moscow’s real aim is to create a military infrastructure in Abkazia.
Tbilisi finally lost control of Abkhazia and South Ossetia in 2008 when the Russian army stepped in to back the regions against a Georgian assault.
The ensuing war caused the worst rift between Russia and the West since the fall of the Soviet Union in 1991.