Japan's key indicator of money supply grew 2.9 percent in April from a year before, an acceleration from the 1.9 percent gain in March, the Bank of Japan said Monday in a preliminary report.

The balance of M2 -- currency in circulation, money in demand-deposit accounts and "quasi" money -- plus certificates of deposit averaged 633.4 trillion yen per day in the reporting month, the central bank said.

The growth rates in the balance have been flagging in recent months as a result of weak cash demand in the private sector.