Japan's inflation rate slowed more than forecast in December, adding to central bank chief Haruhiko Kuroda's challenges in reflating the world's third-biggest economy.

Consumer prices excluding fresh food rose 2.5 percent from a year earlier, the statistics bureau said Friday in Tokyo. That was less than the median projection of 2.6 percent in a Bloomberg News survey of economists. Stripped of the effect of consumption-tax hike last April, core inflation — the Bank of Japan's key measure — was 0.5 percent.

The slide in oil could cause inflation to slow in coming months before helping boost growth and stoking price pressures in the longer term, Kuroda said last week after the Bank of Japan lowered its forecast for the year from April. The BOJ will adjust its monetary stimulus to keep inflation headed toward its 2 percent goal if expectations for price gains among firms and consumers deteriorate, Kuroda said.