Swiss banking giant

UBS

(UBS) - Get Report

said Rory Tapner, chairman and CEO of its Asia Pacific operations, is leaving the company after 25 years and will be replaced by Chi-Won Yoon.

Tapner has held the top post in Asia for five years. UBS didn't provide a reason for Tapner's departure in a press release Thursday.

Tapner's departure is a reminder of UBS's troubles retaining staff as it seeks to return to profitability and deal with the Swiss government, which was forced to shore up the bank in October, the

Wall Street Journal

notes. Since then, UBS's chairman has complained that UBS is having trouble holding on to talented bankers amid criticism of its pay and bonus plans.

Yoon joined UBS in 1997 and was named head of equities and head of fixed income, currencies and commodities for Asia Pacific this year.

"Chi-Won becomes the leader of a business that, under Rory's stewardship over the last five years, has developed into a formidable franchise. Chi-Won's indisputable track-record of commercial success and proven leadership skills will ensure that the firm maintains its focus and continues to enjoy the support of its clients," said Oswald Gruebel, UBS's CEO.

UBS has more than 9,500 employees in Asia Pacific and said it has the largest wealth management business in the region.