BEIJING - China's central bank conducted net cash injections into the market for the fourth straight day on Thursday to ease liquidity strain.

The People's Bank of China (PBOC) conducted 330 billion yuan ($50billion) of reverse repos Thursday, pumping a net 310 billion yuan into the market as 20 billion yuan of reverse repos matured.

Reverse repo is a process by which the central bank purchases securities from commercial banks through bidding with an agreement to sell them back in the future.

Thursday's operation came after a net injection of 150 billion yuan Monday, 140 billion yuan Tuesday and 220 billion yuan Wednesday, as maturing reverse repos and tax payments put pressure on liquidity near the end of the year.