Investor sentiment in the eurozone weakened in October amid budget uncertainty in Italy and concerns over the German auto industry, according to a survey by Frankfurt-based independent research institute Sentix GmbH.

The overall index for the eurozone slipped to 11.4 this month from 12.0 in September. The current situation index fell to 33.0 from 35.0, hitting its lowest level since April 2017; the expectations index improved to negative 8.3 from negative 8.8.

"The reason for the slight decline is probably the discussion about the automobile industry in Germany and the uncertainties about the future fiscal policy of the Italian government," said Manfred Hübner, managing director at Sentix.

Last week, the German government said it wanted the nation's major automakers to provide trade-in incentives and hardware upgrades under its new plan to reduce pollution in major cities, though media reports indicated that not all automakers committed to the retrofits.

In Italy, the EU warned the governing coalition that Rome's budget plans "point to a significant deviation" from the bloc's recommendations.

Meanwhile, Sentix's overall index for the U.S. rose to 25.3 from 23.6, with investors' assessment of the current economic situation reaching an all-time high of 66.5.

Investor sentiment in Asia, excluding Japan, also improved as the overall index climbed to 13.9 from 11.9.

The overall index for the global economy rose to 12.8 from 10.7.

The Sentix survey ran from Oct. 4 to Oct. 6.