The logo of CITIC Securities is seen at its branch in Beijing, China. Its shares surged after Beijing passed a new securities law with a registration-based IPO system

China has fined Citic Securities, Haitong Securities and Guosen Securities for breaking brokerage rules as part of Beijing’s efforts to clean up its financial services sector.

The country’s biggest brokerage Citic Securities Co Ltd said in regulatory filings on Wednesday that it had been fined 308.3 million yuan (US$44.75 million) and warned by the China Securities Regulatory Commission.

China has been trying to clamp down on weak practices in its financial sector, which are seen as a key risk in the development of the world’s second-largest economy.

Moody’s Investors Service downgraded China’s credit ratings for the first time in nearly 30 years on Wednesday, saying it expects the financial strength of the economy will erode as growth slows and debt continues to rise.

Read: China rejects Moody’s reason for first rating cut since 1989

Citic said it had violated regulations related to margin financing and securities lending when handling transactions for Citadel (Shanghai) Trading Company Limited.

Proceeds totalling 61.7 million yuan had been confiscated by the regulator and two executives fined, it added.

Haitong Securities Co Ltd and smaller player Guosen Securities Co Ltd were also punished for violating margin financing rules.

Haitong and Guosen both received warnings and had proceeds from the business confiscated, they said in stock exchange filings.

Haitong was fined 2.5 million yuan, while Guosen and its futures unit were fined a total of 105 million yuan. The regulator also issued warnings and fined the Haitong and Guosen executives involved, the brokerages said.