Moscow, with the Kremlin in the background.

Russia is taking the European Union (EU) to court over sanctions imposed on some of its biggest companies. The move is a sign of the pain that the companies' exclusion from global capital markets is inflicting on the Russian economy.

Rosneft, the state oil company, and Arkady Rotenberg, a long-time friend and former judo sparring partner of President Vladimir Putin, have both launched legal challenges to the sanctions, imposed over Russia's actions in Ukraine.