The Bank of Japan raised its key policy rate to the highest level since 2008 and took a more bullish view on the strength of inflation.

In a well-trailed move, the Bank of Japan on Friday raised the policy rate by 0.25 percentage points, taking it to 0.5 per cent — its highest level in nearly two decades.

Japan's central bank has increased the cost of borrowing to its highest level in 17 years after consumer price rises accelerated in December. The move by the Bank of Japan (BOJ) to raise its short-term policy rate to "around 0.5 per cent" comes just hours after the latest economic data showed prices rose last month at the fastest pace in 16 months.