German investor sentiment unexpectedly improved in September, as investors expect a stop in interest rates hikes.

The ZEW economic research institute on Tuesday reported a rise in its economic sentiment index to -11.4 points from -12.3 points in August.

Analysts polled by Reuters had pointed to an August reading of -15.0.

"The brighter economic prospects for Germany align with a notably more optimistic view of international stock market developments," ZEW president Achim Wambach said.

This is, at least in part, attributed to the increasing proportion of respondents who anticipate stable interest rates in the euro zone and the U.S., he added.

In contrast, the assessment of the current economic situation in Germany continues to worsen considerably. The indicator fell to -79.4 points, the lowest value in three years.

"This development puts into perspective the slight improvement in expectations regarding Germany's economic situation over the next six months," Wambach said. (Reporting by Miranda Murray and Maria Martinez, Editing by Friederike Heine, editing by Ed Osmond)