The central bank will increase the pace at which it expands base money to 80 trillion yen (£454bn) a year, instead of 60-70 trillion yen. It also intends to triple its purchase of exchange-traded funds (ETFs) and real estate investment trusts (REITs), and extend the duration of its portfolio of Japanese government bonds.

These unexpected steps are intended as a pre-emptive move to boost inflation in an effort to reach the bank’s 2% inflation target by April 2015.

Data released earlier on Friday showed Japan’s annual core consumer inflation slowed for a second month in a row in September. Meanwhile, consumer spending fell and unemployment rose last month.

After the market closed on Friday, the BoJ also released its latest economic outlook, where it halved its growth forecast for the current fiscal year to just 0.5% as a result of weakening consumer demand.

The surprise move caused the Nikkei 225 index to rally 4.8% on Friday, while the yen fell to its lowest level in seven years against the US dollar to trade at 111.29 yen per dollar.

According to reports, the Bank’s Governor Haruhiko Kuroda said today the BoJ would consider further easing if needed.

The move comes as the US Federal Reserve turns off the QE tap. On Wednesday the central bank confirmed it had ended its final $15bn in monthly asset purchases, following a tapering process that began in December last year.