BEIJING, June 9 -- China's consumer price index (CPI), a main gauge of inflation, was down 0.1 percent year on year in May, official data showed on Monday.

On a monthly basis, the CPI dipped 0.2 percent last month, according to the National Bureau of Statistics (NBS).

The core CPI, which excludes food and energy prices, climbed 0.6 percent year on year in May, accelerating from a rise of 0.5 percent registered in April.

For the January-May period, the country's CPI averaged a 0.1-percent decline compared with the same period last year, according to the NBS.