China's value-added industrial output, an important economic indicator, expanded 6 percent year on year in April, retreating from the 6.8-percent increase for March, official data showed Saturday.

In the first four months, industrial output rose 5.8 percent from a year earlier, according to the National Bureau of Statistics (NBS).

Industrial value-added output measures the output of Chinese companies with annual revenues above 20 million yuan (3.3 million U.S. dollars).

Industrial production accounted for 40.5 percent of China's total GDP in 2015, making it one of the leading indicators of economic growth.

The NBS attributed the slower growth to weak demand, slower growth in mining sectors and industries with severe overcapacity as well as the rising prices of commodities.

In breakdown, industrial production in eastern regions climbed 5.9 percent in April. Central and western regions both rose faster, 7.1 percent and 7.3 percent up on the previous year, respectively.

Manufacturing output expanded 6.9 percent in April. Mining output rose 0.1 percent and the output of the electricity, heating, gas and water sectors grew 1.9 percent, the NBS said.

Despite the slower growth, the progress in structural reforms is evident, said NBS senior statistician Jiang Yuan.

Output of the hi-tech and pharmaceutical sectors maintained strong growth, rising 9.7 percent and 10.7 percent, respectively.

In addition, the output of new energy vehicles and industrial robots grew 140 percent and 16.5 percent, respectively, pointing to an upgrade of consumption, said Jiang.