BERLIN, June 15 (Reuters) - Former Commerzbank board member Jochen Kloesges is to take over as Chief Executive of Aareal Bank AG, the property finance firm said on Tuesday, after months of searching for a new boss.

The 56-year-old is expected to take office on Sept. 15, said Aareal Bank after its supervisory board agreed on the appointment. Aareal is under pressure from an activist investor over its strategy.

Former Aareal CEO Hermann Merkens left last autumn for health reasons. The bank also announced that board member Thomas Ortmanns would leave the bank at his own request on 30 September.

Kloesges left Commerzbank in 2013.

(Reporting by Patricia Uhlig Writing by Madeline Chambers Editing by Riham Alkousaa)