ZURICH (Reuters) - Siemens could cut up to 5,000 jobs worldwide in its struggling factory automation business, Chief Executive Roland Busch said on Thursday.

"Sometimes we have to do some re-engineering because the developments weren't as positive as we expected them to be," said Busch after Siemens reported a 46% plunge in profit at its flagship digital industries business.

"This means we are going to have a low- to medium-sized four-digit amount which will affect some areas," Busch said.

No exact figure for the job figures has yet been decided, said Siemens, which employs 70,000 in digital industries globally.

Busch added that he saw long-term potential for the automation market, due to shrinking populations and the low level of mechanization at small and medium-sized companies.

(Reporting by John Revill and Alexander Huebner; Editing by Miranda Murray)