The People's Bank of China (PBOC), the central bank, auctioned 22 billion yuan (3.2 billion U.S. dollars) worth of three-year bills on Thursday at a yield of 2.68 percent.

The move came after the central bank sold 55 billion yuan of one-year bills in its regular open market operations on Tuesday.

As 144 billion yuan of central bank bills and repurchase agreements matured this week, the central bank actually injected a total of 67 billion yuan into the market, the sixth straight week of cash injection.

The PBOC has injected 783 billion yuan into the interbank market since late May to help ease the tight money supply situation.