The Bank of Japan (BoJ) has extended its asset purchasing programme by 10 trillion yen ($126bn; £78bn), following similar moves by the Federal Reserve and the European Central Bank.
The move, aimed at boosting the Japanese economy, increases the overall size of the stimulus programme to 80 trillion yen.
Although the increase had been anticipated by some analysts, many were surprised by the size of it.
Finance Minister Jun Azumi said the BoJ “took more action than we anticipated”.
Under the asset purchasing programme the central bank buys bonds in order to keep the long-term cost of borrowing down.