The partly state-owned bank, which has been targeted by activist U.S. private equity fund Cerberus, is trying to regain its footing after the resignations earlier this summer of its chief executive and chairman, and years of setbacks since the financial crisis.

The bank has a new chairman, who has begun the search for a new CEO.

Mandel had been a proponent of an extensive branch network, but the lender has shuttered 200 of around 1,000 branches and is now discussing the closure of hundreds more.

The decision to accept the resignation offer from Mandel was made at a meeting of the bank's supervisory board on Thursday.

Sabine Schmittroth will assume responsibility for the private client business for now, the bank said.

(Reporting by Tom Sims; Editing by Michelle Adair)