China's major industrial firms posted steady profit growth in the first half of the year, further evidence of firming strength in the economy, official data showed Thursday.

The companies reported a 22-percent profit increase in the first six months from one year earlier, slowing from 22.7 percent in the January-May period but much faster than the 8.5-percent increase in 2016, the National Bureau of Statistics said in a statement.

In June alone, profits of major industrial firms rose 19.1 percent year on year, faster than the 16.7-percent rate in May, it said.