SHANGHAI: China stocks dropped the most in six weeks on Wednesday following Wall Street's tech rout, with heightened Sino-US tensions and falling oil prices also curbing risk appetite.

Some stock investors rotate into bonds amid signs of tighter regulatory scrutiny and climbing yields.

The blue-chip CSI300 index fell 2.3% to 4,584.59 points, posting its biggest one-day percentage drop since July 24. The Shanghai Composite Index lost 1.9% to 3,254.63 points.

Shenzhen's start-up board ChiNext, which is up more than 40% this year, slumped 4.8%.

Wall Street closed lower on Tuesday as heavyweight technology names extended their sell-off to a third straight session, sending the Nasdaq into correction territory. Adding to the gloom, oil prices hit lows not seen since June.

A sell-off in high-flying US technology shares, fuelled partly by concerns about excess purchases of call options, has increased the risk of a larger correction across other markets.

Investors are also circumspect ahead of the November US President election, with Donald Trump expected to rachet up pressure on China as part of his campaign strategy.

Chinese semiconductor shares continued to slide as a possible US sanction against Chinese chip-making giant SMIC cast a pall over the sector.

Shanghai-listed shares of Semiconductor Manufacturing International Corp plunged 6%. Should the ban occur, more than half of SMIC's sales could be affected, potentially dealing a bigger blow to Chinese equipment and materials players, brokerage CLSA wrote in a note.

Sentiment in China was also hurt by signs that regulators are stepping up crackdown on speculation. Three high-flying stocks listed on the ChiNext market suspended trading on Wednesday, citing investigations into "abnormal volatility".

"It's time to swap stocks for bonds," said Li Bei, fund manager, Banxia Investment.

"Currently, A-share valuations are purely supported by risk appetite, which is totally unreliable. Reversal of sentiment can happen at any time," she wrote on Wednesday.