The selling seemed to be aimed at stabilising the yuan, with the swaps helping procure dollars as well as anchoring the price of yuan in forwards, the sources, who have direct knowledge of market trades, told Reuters.

The yuan is down 11.6% versus the dollar this year. It was trading around 7.1980 per dollar on Monday, while the one-year forwards had fallen to 6.95.

(Reporting by Shanghai and Beijing Newsroom; Editing by Ana Nicolaci da Costa)