A closely watched survey shows that the economy of the 19-country eurozone lost momentum in September as businesses fretted over the potential impact of a series of political uncertainties.

Financial information company Markit said Wednesday that its purchasing managers' index, a broad gauge of economic activity, dropped to a 20-month low of 52.6 points in September from 52.9 the previous month.

As anything above 50 indicates expansion, Markit said its index indicates the eurozone economy grew by a muted quarterly rate of 0.3 percent in the third quarter.

Chris Williamson, IHS Markit's chief economist, said slowing growth reflects "growing caution" among businesses linked in many cases to political uncertainty.

He expects this to persist next year, noting elections in Germany and France and how Britain exits the European Union.