BEIJING, June 9 -- China's consumer inflation dipped in May due to lower energy and food prices, while the factory-gate price decline extended, official data showed Monday.

The consumer price index (CPI), a main gauge of inflation, edged down 0.1 percent year on year in May, according to the National Bureau of Statistics (NBS).

On a monthly basis, the CPI dipped 0.2 percent last month.

Falling energy prices, which contributed 0.47 percentage points to the year-on-year decline in the CPI last month, were the main drag on the country's CPI, NBS statistician Dong Lijuan said.

Dong noted that positive changes emerged in some sectors as the country's policies to boost consumption continued to take effect.

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, according to the NBS.

A breakdown of the data showed that food prices declined 0.4 percent year on year last month, non-food prices remained flat, consumer goods prices dropped 0.5 percent, while service prices rose 0.5 percent.

During 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.

Monday's data also showed that China's producer price index (PPI), which measures costs for goods at the factory gate, went down 3.3 percent year on year in May. The decline widened from a fall of 2.7 percent in April.

Dong attributed the PPI decline to falling international crude prices, which pulled down domestic prices in petroleum-related industries, along with a seasonal slowdown in demand for energy and raw materials. Dong noted that coal prices eased and construction activity was disrupted by hot and rainy weather in southern regions.

On a month-on-month basis, the PPI dropped 0.4 percent in May, according to the NBS data. In the first five months of the year, the PPI on average declined 2.6 percent compared with one year earlier.