The nation's annual core consumer inflation ticked up slightly in August but remained distant from the Bank of Japan's 2 percent target, suggesting that monetary policy will stay ultraloose for the time being.

The proportion of items in the inflation gauge that rose in price last month hit its lowest in nearly five years, underscoring the challenge the central bank faces in wiping out the country's entrenched deflationary mindset.

Soft inflation could pose a challenge for Prime Minister Shinzo Abe's efforts to put a sustained end to deflation as he heads into a third term, though he has recently distanced himself from the BOJ's elusive target.