BEIJING, May 22 (Xinhua) -- China's rail freight volume, an indicator of economic activity, registered healthy growth in the first four months of this year, official data showed Tuesday.

Railways carried 1.29 billion tonnes of cargo in the Jan.-April period, up 6.1 percent from a year earlier, according to figures from the National Bureau of Statistics (NBS).

In April alone, rail freight volume was up 1.4 percent year on year to 305.5 million tonnes.

Steady growth in rail freight transportation served as a further sign of sound economic momentum.

In the first four months, China's industrial output rose 6.9 percent year on year, accelerating from a 6.8-percent gain in the first quarter, earlier NBS data showed.

China's fixed-asset investment in railways reached 141 billion yuan (about 22.1 billion U.S. dollars) in the first four months, marking an 8.6-percent decrease year on year, according to the National Railway Administration.