China stocks suffered their biggest one-day percentage drop in more than six and a half years, dragged down by record tumbles in financial stocks as authorities battled excessive market speculation.

Regulators cracked down on margin trading, which has been blamed for fuelling a wave of speculation over the past three months.

Bank stocks were hit after the banking regulator issued draft rules to tighten supervision of entrusted loans, a kind of shadow banking.

The banks sub-index plummeted 9.97 per cent and the financial sub-index sank 9.62 per cent.

All China CSI300 stock index futures were down at least 10 per cent, except the September index which dove 12 per cent.

The CSI300 index of the largest listed companies in Shanghai and Shenzhen fell 7.7 per cent, to 3,355.16. The Shanghai Composite Index also lost 7.7 per cent, to 3,116.35 points.

The falls were the biggest for both indexes since June 10, 2008.

Among the most active stocks in Shanghai were Bank of China , down 10.0 per cent to 4.48 yuan; Agriculture Bank of China, down 9.9 per cent to 3.55 yuan and ICBC , down 9.9 per cent to 4.64 yuan.

In Shenzhen, BOE Technology , down 8.5 per cent to 3.01 yuan; TCL Corp, down 7.7 per cent to 3.71 yuan and Guosen Securities, down 10.0 per cent to 21.31 yuan were among the most actively traded.

Foreign investment flowing into Shanghai from Hong Kong through the mutual market access pilot programme took up -0.33 billion yuan of the 13 billion yuan daily quota.

Total volume of A shares traded in Shanghai was 40.0 billion shares, while Shenzhen volume was 19.5 billion shares.

Reuters