Japan's monetary base soared 31.6 percent in May from a year earlier to ¥154.14 trillion, marking a record high for a third straight month, the Bank of Japan said Tuesday, as it continued injecting money into the market under its aggressive easing policy.

The average daily balance of liquidity provided by the BOJ — consisting of cash in circulation and the balance of current account deposits held by commercial financial institutions at the bank — expanded for the 13th straight month.

The country's monetary base at the end of May stood at ¥159.16 trillion, the highest level ever, the BOJ said.

The balance of current account deposits — the sum of funds the institutions can use freely — more than doubled to ¥66.31 trillion, with the BOJ injecting more liquidity into the banking system by buying a large number of financial assets from banks.