The missing pieces of artwork include pictures, icons, sculptures, metalwork, gems, military decorations, vintage armor, and rare books. Some of them were stolen from museums and churches, but most from private houses.
The biggest challenge is to track down pieces that have been smuggled out of the country, investigators said.
In 1994, seven Orthodox icons were stolen from a museum in the northwestern Russian town of Ustyuzhina. One of the icons - a 16th-century image of the Blessed Virgin Odigitria - was purchased by the owner of a London art gallery from a Russian immigrant living in Germany for 60,000 pounds sterling. A Brussels-based collector then bought the icon for 170,000 pounds, agreeing that it would continue to be displayed in London.
This year the icon was finally tracked down and brought home as the result of a joint operation by Russian police, the ministries of culture and media, and Interpol. Police are still working to identify those behind the crime and bring them to justice.
