The Interior Ministry announced in a statement on Thursday that it had accepted the resignation of Manfred Schmidt, head of the Federal Office for Migration and Refugees (BAMF).

The ministry cited "personal reasons" for Schmidt's departure from Germany's top migration authority.

Earlier this month, Schmidt was criticized by the German opposition party SPD for not responding to applications for asylum quickly and for not expanding his office's capacity to handle the refugee crisis.

The BAMF is said to have more than 250,000 unprocessed asylum applications with the average turnaround time averaging more than five months, a stark difference to Germany's neighbor the Netherlands, which handles cases in an average of eight days.

The decision comes amid Germany's largest refugee crisis since World War II, with some 800,000 to 1 million refugees expected this year alone, five times the previous year's total.

German Interior Minister Thomas de Maiziere thanked Schmidt for the "extraordinary work" he completed during his tenure as Germany's migration chief.

Schmidt held the office since December 2010.

ls/jil (Reuters, AP, dpa)