BEIJING - China's central bank drained 150 billion yuan ($21.7 billion) from the market Wednesday.

The central bank conducted 30 billion yuan in seven-day reverse repos, 20 billion yuan in 14-day reverse repos and 20 billion yuan in 28-day reverse repos.

A reverse repo is a process where central banks purchase securities from banks, with an agreement to sell them back in the future.

With 220 billion yuan worth of reverse repos maturing Wednesday, the central bank effectively withdrew 150 billion yuan from the market.

The central bank has increasingly relied on open-market operations for liquidity, rather than cuts in interest rates or reserve requirement ratios to maintain monetary policy.

Analysts said liquidity is expected to remain tight in the near term, as China will continue to keep a prudent monetary policy.

The benchmark overnight Shanghai Interbank Offered Rate, a measure of the cost at which Chinese banks lend to one another and a key barometer of liquidity, fell for the fifth straight trading day Wednesday from a two-month high on December 1.