PMI pushes mainland stocks lower

SCI falls 1.8%, extending annual loss to 24% ahead of disappointing company earnings

Mainland stocks extended the steepest monthly sell-off since the global financial crisis after an official factory gauge slumped to a three-year low, some of the nation's largest companies warned of disappointing earnings and traders unwound margin debt.

The Shanghai Composite Index slid 1.8 percent to 2,688.85 at the close, extending its loss this year to 24 percent. PetroChina Co, which has the biggest weighting on the benchmark gauge, dropped after saying annual net income probably fell as much as 70 percent. Leveraged bets on Chinese stock exchanges fell for a record 21st day on Friday to the lowest level since last year's rout.