By Maria Martinez

BERLIN (Reuters) - German investor morale improved more than expected in October, the ZEW economic research institute said on Tuesday, reporting a rise in its economic sentiment index to 13.1 points from 3.6 points in September.

Analysts polled by Reuters had pointed to a reading of 10.0.

The contributing factors for the rise include the expectation of stable inflation rates and the associated prospect of further interest rate cuts by the European Central Bank, ZEW president Achim Wambach said.

Positive signals are also coming from Germany's export markets, with economic expectations for the eurozone, the United States and China also significantly improving, he added.

While the indicator of economic sentiment improved, the assessment of the economic situation fell to minus 86.9 points from minus 84.5 in the previous month.

Almost nine out of 10 respondents assessed the current economic situation as negative, the survey showed.

(Reporting by Rachel More, Miranda Murray and Maria Martinez; Editing by Madeline Chambers)