BEIJING - China's national rail freight volume, an indicator of economic activity, fell significantly amid an economic slowdown in 2015, official data showed on Tuesday.

Railways carried 3.36 billion tons of cargo last year, down 11.9 percent year on year, compared with a fall of 3.9 percent in 2014, the National Development and Reform Commission (NDRC) said.

NDRC said rail freight volume fell 13.4 percent from one year earlier in the last quarter of 2015, with the drop easing slightly from the third-quarter's 13.9 percent decrease.

The tepid reading came after China posted its weakest economic growth in 25 years in 2015, which was weighed down by weak demand both at home and abroad, industrial overcapacity and faltering investment.

By comparison, the country's passenger traffic volumes continued robust growth, with its railway passenger volume up 10 percent from a year earlier in 2015. Air transportation passenger volume rose 10.4 percent year on year.