The People's Bank of China, the country's central bank, has fined institutions and individuals responsible for detected irregular trading practices, intensifying its oversight of the interbank bond market amid a bull trend to maintain market order.

The PBOC said on Monday that three institutions were found to have engaged in bond market violations as recent investigations revealed misconduct such as improper account lending and actions designed to bypass regulatory and internal control requirements.

The actions came as China's bond market continues to attract global interest. As of the end of November, a total of 1,156 overseas investors had entered the Chinese onshore bond market, holding bonds worth 4.2 trillion yuan ($575.4 billion), according to the central bank.

While the bond market has seen a bull trend over the past two years, resulting in substantial profits for financial institutions' fixed-income businesses, the PBOC's actions signal its commitment to safeguarding market order and promoting the high-quality development of the bond market.

Having established a routine monitoring and enforcement mechanism for the interbank market this year, the central bank said that it will support legitimate and compliant transactions while maintaining a "zero-tolerance" stance toward illegal activities.