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

The growth was higher than market expectations of around 6.4 percent for the period.

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.

A breakdown of the data showed that the industrial structure continued to improve, with production in high-tech industries and the equipment manufacturing sector expanding by 11.8 percent and 10.3 percent, respectively, last month.

Output of new energy vehicles saw a surge of 82.2 percent year on year during the period, while industrial robot production jumped by 35.4 percent, NBS data showed.

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).