The key unsecured overnight call rate in the short-term money market stood at 0.3 percent Thursday morning, higher than the Bank of Japan's target of 0.25 percent.
Some money brokers attributed the firm fund demand partly to the planned drainage of 400 billion yen from the market at 1 p.m. Thursday with the expiration of a commercial paper operation.
The benchmark rate's weighted average was 0.27 percent on Wednesday when the BOJ took its first "neutral" stance since February 1999, leaving a zero surplus in banks' BOJ reserve accounts.
At its regular market operation time Thursday morning, the BOJ supplied 700 billion yen by purchasing bills.
The central bank later supplied an additional 300 billion yen through a bill-buying operation, a move that is expected to have left banks' accounts at the BOJ with 700 billion yen more than the previous day.
Despite the supply of funds, the unsecured overnight call rate only briefly dipped to 0.27 percent. Most banks traded the key loan at 0.3 percent as fund demand stayed strong, traders said.