The sculpture, called "Peace and Labor", was put up in a central square in the Barents Sea town of Severodvinsk some 20 years ago to mark the city's 50th anniversary, the city administration said. The 30-meter-high sculpture, commissioned by local shipyards, included three flagstaffs and figures of shipyard workers at its basement.
Local authorities said metals hunters had only recently discovered that the sculpture, painted black, was covered with copper.
"Considering those people's zeal in searching for metal, we are afraid the flagstaffs will be the only components of the sculpture that will survive," an official said.
Severodvinsk's mayor has ordered police to include the square in their patrol routes and put forward proposals to illuminate the sculpture.
Many Soviet-era metal monuments have fallen victim to metals hunters in the post-Soviet period. In some areas, people have even been reported to have cut off power lines.