China's central bank on Friday injected 149 billion yuan ($21.7 billion) into the market via medium-term lending facility (MLF) to maintain ample liquidity.

The funds will mature in one year with an interest rate of 3.3 percent, unchanged from previous operations, the People's Bank of China (PBOC) said on its website.

The MLF tool was introduced in 2014 to help commercial and policy banks maintain liquidity by allowing them to borrow from the central bank using securities as collateral.

No other open market operations were conducted on Friday.

The PBOC will make policies more forward-looking, flexible and effective, maintain proper control over the floodgate of money supply and keep liquidity at a reasonable and abundant level, according to a quarterly report released earlier this month.

China's prudent monetary policy will be "kept neutral and be neither too tight nor too loose," said the report.