BERLIN, Sept 16 (Reuters) - Germany put under trusteeship on Friday the German subsidiary of Russian energy company Rosneft, handing to the federal regulator control of the PCK refinery in Schwedt that is a key source of fuel for Berlin.

"With the trusteeship, the threat to the security of energy supply is countered and an essential foundation stone is set for the preservation and future of the Schwedt site," the Economy Ministry said in a statement.

Rosneft Deutschland accounts for about 12% of Germany's oil processing capacity and is one of the largest oil processing companies in the country, the ministry added.

(Reporting by Paul Carrel; Editing by Clarence Fernandez)