Bloomberg, citing unidentified people with knowledge of the matter, said the timing and size of the investment was unclear. The investment would likely come through Qatar Investment Authority, the sovereign wealth fund, the report said.

A spokesman for Deutsche Bank declined to comment. A representative for Qatar Investment Authority wasn't immediately available for comment.

The Qatari royal family already holds a 6.1 percent stake in Deutsche Bank, according to the bank's website.

The Qatar Financial Centre released a statement in December distancing itself from a newspaper report that said it planned to raise its stake in Deutsche Bank.

(Reporting by Tom Sims; Editing by Christoph Steitz and Hugh Lawson)