Profits of China's major industrial firms grew 13.6 percent year on year in the first 10 months of 2018, down from the 14.7-percent expansion for the January-September period, the National Bureau of Statistics (NBS) said Tuesday.

Profit in 34 of the 41 sectors surveyed increased compared with one year earlier, unchanged from that for January-September, according to the NBS.

In October, combined profits at industrial firms with an annual revenue of more than 20 million yuan (about 2.88 million U.S. dollars) rose 3.6 percent year on year to 548 billion yuan, 0.5 percentage points lower than that recorded in September.

According to the NBS, the sectors of steel, construction materials, oil and chemicals contributed 75.7 percent to the overall industrial profit increase.

By the end of October, the debt-asset ratios of major industrial firms dropped 0.5 percentage points from a year earlier to 56.7 percent.

NBS official He Ping attributed the slowdown in October to slower growth in industrial production and product prices, as well as a high comparative base last year.

Operating costs and leverage ratios for industrial companies kept falling amid slower growth in industrial profits, while their profitability continued to improve, he noted.

In early November, the NBS reported China's value-added industrial output, an important economic indicator, saw slightly faster growth in October than the previous month.

The output expanded 5.9 percent year on year last month, up 0.1 percentage point from that recorded in September.

Industrial output, officially called industrial value added, is used to measure the activity of designated large enterprises with an annual revenue of at least 20 million yuan.