Japan's key composite index rose in December following a fall the previous month, the government said on Friday, suggesting the country's economy may have overcome the negative impact of the 3-percentage-point consumption tax hike to 8 percent last April.

The December index of coincident indicators, such as industrial output, retail sales and new job offers, advanced 1.5 points to 110.7 from the previous month, against the 2010 base of 100, the Cabinet Office said in a preliminary report.

The government upgraded its basic assessment of the coincident index, saying it suggests the economy is "improving." The assessment is defined as indicating the likelihood of economic expansion.