SINGAPORE - Business sentiment among Asia's top companies fell sharply in the third quarter, found a new survey by Thomson Reuters and Insead.

They were weighed down by worries about China's slowing economy, a possible end to the United States Federal Reserve's stimulus policy, and a decline in the outlook for regional economic hubs like Singapore.

The Thomson Reuters-Insead Asia Business Sentiment Index fell to 66 in the third quarter, from 74 in the previous quarter.

A reading above 50 indicates an overall positive outlook, and the survey noted this is its steepest decline in three years.

Singapore also turned in a reading of 50 for the quarter, a sharp drop from the previous quarter's score of 67.

The index surveyed 200 of the Asia-Pacific region's top companies in 11 economies across sectors including financial, property, resources, and technology.

Companies polled include Australian construction materials firm James Hardie Industries, Japan's Fast Retailing, and Indian drugmaker Lupin.