BEIJING, May 15 (Xinhua) -- China's industrial output expanded 7 percent in April, quickening from the 6-percent rise in the previous month, official data showed Tuesday.

In the first four months, industrial output rose 6.9 percent, compared with the 6.8-percent gain in the first quarter, the National Bureau of Statistics (NBS) said in a statement.

Industrial output, officially called industrial value added, is used to measure the activity of designated large enterprises with annual turnover of at least 20 million yuan (about 3 million U.S. dollars).