The People's Bank of China (PBoC) has devaluated the yuan for the second day. China's central bank set Wednesday's daily fixing at 6.3306 per U.S. dollar, down from 6.3231 on Tuesday.

The PBoC said on Tuesday that it was a "one-off depreciation".

"Looking at the international and domestic economic situation, currently there is no basis for a sustained depreciation trend for the yuan," the central bank said on Wednesday.

A weaker yuan should help to boost the activity in the manufacturing sector and exports, which dropped 8.3% year-on-year in July.