The Bank of Japan pumped a record 1.5 trillion yen into the money market Monday morning in an effort to stem the rise in the unsecured overnight call money rate.
Following the open-market operations, the benchmark short-term interest rate dropped to 0.070 percent to 0.080 percent from earlier levels of around 0.100 percent.
Under the BOJ's zero-interest-rate policy, the central bank treats 0.100 percent as the upper limit for the call rate.
The call rate has been rising since the BOJ ended its five-year-old "quantitative easing" policy in March.
With the policy shift, the outstanding balance of current accounts financial institutions have at the BOJ has dropped, tightening the money supply and putting upward pressure on short-term rates. The BOJ aims to lower the balance of current-account deposits to below 10 trillion yen by month end.