Core inflation remained subdued in May, yet again highlighting how far off the Bank of Japan is in hitting its 2 percent price goal despite over five years of massive stimulus.

The stubbornly weak inflation is also another reason why the central bank is widely expected to take some time before exiting its ultraeasy monetary policy, even as the U.S. Federal Reserve and the European Central Bank are far down the road in rolling back crisis-era policies.

The core consumer price index, which includes oil products but excludes volatile fresh food prices, rose 0.7 percent year-on-year in May, unchanged from April, and matching economists' median estimate, Ministry of Internal Affairs and Communications data showed on Friday.