Russian billionaires brought in by the Kremlin to support the $10.6bn (€8.5bn) stock market listing of Rosneft nearly 18 months ago have reduced their stakes in the state-controlled energy company.

The group of billionaires, which includes Chelsea football club owner Roman Abramovich and mining tycoons Vladimir Lisin and Oleg Deripaska, has sold Rosneft shares worth between $700m and $800m, according to a Deutsche Bank analyst report.