Hong Kong shares on Thursday morning tracked US markets lower, as worries about global economic growth resurfaced. China's blue-chip CSI300 index fell 0.2 per cent, to 3202.33 points by the lunch break, while the Shanghai Composite Index lost 0.3 per cent, to 2983.06 points. In Hong Kong, the Hang Seng index dropped 0.4 per cent, while the Hong Kong China Enterprises Index lost 0.9 per cent. China's robust market rebound since early March appears to be losing momentum as trading volumes have shrunk and the SSEC fails to stand decisively above the 3000 mark - seen by many as a key psychological level. Worries are mounting that the country's debt-fuelled recovery in the first quarter could be short-lived, amid signs that fresh liquidity has failed to energise China's economic muscles, with the spill-over boosting property and commodity prices instead. A private survey showed on Thursday that activity in China's services sector expanded in April, but the gains were slightly less robust than in March. Most sectors in China fell, but airline stocks surged after China's central government on Wednesday unveiled plans to promote airline transportation by pledging to open up low-altitude air space. China's biggest carriers, including Air China Ltd, China Eastern Airlines and China Southern Airlines all jumped more than 3 per cent. In Hong Kong, sentiment was soured by overnight weakness on Wall Street, where major share indexes declined in the wake of weak job and worker productivity data.