A bond market regulator in China warned Citic Securities and Industrial Bank on Friday against charging bond underwriting fees way below normal levels in the market, calling this "improper competitive behaviour".

The two firms charged commissions less than the average cost of running the underwriting business, National Association of Financial Market Institutional Investors (NAFMII), which oversees the interbank bond market, said in a statement.

(Reporting by Noah Sin and Samuel Shen; Editing by Andrew Heavens)