BEIJING, May 9 -- China's producer price index (PPI) contracted 2 percent year on year in April, following a 2.3-percent decline in March, pointing to weakness of the economy, National Bureau of Statistics (NBS) data showed on Friday.

The index, which measures inflation at wholesale level, edged down 0.2 percent in April from the previous month, said the bureau.

Among the 30 main industries surveyed, 14 sectors including power generation and oil refining posted month-on-month price increases in April. Sixteen sectors including non-ferrous metal smelting and coal exploitation posted month-on-month price drops, said Yu Qiumei, a senior statistician with the NBS.

The Consumer Price Index (CPI), a main gauge of inflation at retail level, increased 1.8 percent year on year in April, down from 2.4 percent in the previous month, said the bureau.

The two inflation readings reflect the weakness of demand including in both consumption and investment, said Lu Ting, chief China economist with Bank of America Merrill Lynch, in a research note.

China's gross domestic product (GDP) expanded 7.4 percent in the first quarter, as slower property investment and exports weighed on broader economic growth during the period.