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.

"China's economy maintained its trend of steady development in April," NBS spokesperson Liu Aihua said.

However, it is worth noticing that the economy faces growing external uncertainties and acute problems of unbalanced and inadequate domestic development, Liu added.

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).

Output in the mining sector fell 0.2 percent year on year amid a government drive to restructure and optimize the industry.

China plans to cut ineffective steel capacity by 30 million tonnes and coal capacity by 150 million tonnes in 2018, according to a government work report released earlier this year.

Ownership analysis showed that industrial output of state-holding enterprises was up 7.7 percent, while industrial output of enterprises funded by overseas investors increased 6.8 percent.

NBS data also showed that China's retail sales of consumer goods grew 9.4 percent year on year to reach 2.85 trillion yuan in April.

China's fixed-asset investment rose 7 percent in the first four months of the year, down from 7.5 percent for January-March.