China's securities regulator said on Friday it had published rules on the fund of funds (FOF) business and would strengthen supervision of the market.

FOF, also referred to as multi-manager investment, is a strategy of holding a portfolio of other investment funds rather than investing directly in stocks, bonds or other securities.

According to the rules, an FOF must invest at least 80 percent of its assets in mutual funds, while management and custodian fees must not be charged twice, the regulator said on its official microblog.

The China Securities Regulatory Commission (CSRC) said it will strengthen supervision of the business and protect the interest of investors in FOFs.