Japanese manufacturing activity expanded at a slower pace in September, a survey showed on Thursday, as new export orders tumbled the most in almost three years in a worrying sign that China's faltering economy is hurting global demand. The Markit/Nikkei Japan Flash Manufacturing Purchasing Managers Index (PMI) stood at a seasonally adjusted 50.9 in September from a final 51.7 in August. The index remained above the 50 threshold that separates expansion from contraction for the fifth straight month but fell for the first time in three months. Japan's lacklustre PMI may add to concerns about the global economy after a survey on Wednesday showed China's flash manufacturing PMI in September unexpectedly fell to a 6 1/2-year low. Worryingly, the flash index for new export orders in the world's third-biggest economy slipped to 47.8, from a final 51.6 in the previous month to show the biggest contraction since February 2013. A number of respondents cited China as a reason for slowing sales and shipments, highlighting how deeply China's slowing economy is starting to impact global demand and hitting export-reliant countries like Japan. The index for new orders fell to a preliminary 52.0 from 53.4 in August in a sign that domestic consumption also could be losing some momentum. The PMI could reinforce expectations of a tepid rebound in July-September gross domestic product after the economy contracted an annualized 1.2 percent in the second quarter as exports slumped and consumers cut back spending.