Business activity in the eurozone picked up again to hit a three-month high in August, although concerns remained over new orders and business sentiment, a key survey showed Thursday.

The HCOB Flash Eurozone composite purchasing managers' index (PMI) -- a key gauge of the overall health of the economy -- rebounded to 51.2 in August, up from 50.2 in July. Any reading above 50 indicates growth, while a figure below 50 shows contraction.