HNA's buy, which one trader said would lift confidence in the lender's stock, leaves roughly one fifth of the struggling bank in the hands of investors who may be pursuing strategic interests.

It comes at a time of heightened uncertainty at the bank, as it grapples with a strategic turnaround, an uncertain global economy and the impact of Britain's departure from the European Union.

HNA's stake puts it slightly ahead of Qatari investors. Funds controlled by Qatar's former Prime Minister Sheikh Hamad bin Jassim al-Thani last year increased their stake, including options, to just under 10 percent.

The Chinese group has been on an acquisition spree, expanding from its traditional business of aviation and logistics into financial services, betting on asset managers and consumer finance for growth at home and overseas.

It reflects a broader push by China into financial services globally as Beijing encourages its corporate sector to expand overseas, although it faces increased regulatory scrutiny in the United States and Europe.

Hefty legal penalties including for the sale of toxic U.S. mortgage debt have hit Deutsche Bank hard and even prompted speculation last year, denied by the bank, that it needed a government bailout.

Last month it asked investors to for an 8 billion euro cash injection, the fourth such request since 2010, putting it on track to raise more than its entire market value over roughly seven years.

HNA last lifted its stake in Deutsche in March to 4.76 percent. A regulatory filing with the U.S. Securities and Exchange Commission said it had now increased this to 9.9 percent.

Fund manager BlackRock owns 6.1 percent.

(Writing by John O'Donnell and Emma Thomasson)

By Alexander Hübner and Arno Schuetze

Stocks treated in this article : BlackRock, Inc., Deutsche Bank AG, HNA Holding Group Co Ltd