Germany's Commerzbank AG (CBK.XE) said Thursday management board member Achim Kassow will leave the company July 12 to become chief executive of Oldenburgische Landesbank, a unit of Allianz SE (ALV.XE).

Ulrich Sieber, 45, management board member for human resources and integration of Dresdner Bank, will in addition assume responsibility for the bank's business in Central and Eastern Europe, which is currently Kassow's job, the bank said.

Kassow, 44, is leaving the bank at his own request, Commerzbank said.

Oldenburgische Landesbank is the largest private regional bank in Germany, and through its Allianz Bank branch offers banking services for customers and representatives of Allianz in Germany.

"Achim Kassow has made a major contribution to the success of the bank," said Klaus-Peter Mueller, chairman of Commerzbank's supervisory board. "He was responsible for the strategic disinvestments in asset management, has clearly expanded our market position in the private customers business, and attained the turnaround with our business in Central and Eastern Europe."

Kassow has been a member of the management board since November 2004. Before that, he was chief executive of Commerzbank's online bank comdirect for two years.

Sieber has been Member of Commerzbank's management board since June 2009.

Kassow will succeed Benedikt Buhl as chief executive of Oldenburgische Landesbank. Oldenburgische Landesbank said Buhl, CEO since the beginning of 2009, has requested that the supervisory board relieve him from duty from May 19. The bank said Buhl is leaving Oldenburgische Landesbank by mutual consent due to different views on the bank's future strategy.

-By Ulrike Dauer, Dow Jones Newswires; +49 69 29725 500; ulrike.dauer@dowjones.com