China's working-age population declined for the first time in recent decades in 2012, the government said Friday, as it detailed the extent of the demographic time bomb the country faces.

China introduced its controversial one-child policy in the late 1970s to control population growth, but its people are now ageing, moving to the cities, and increasingly male, government statistics showed.

The world's biggest national population rose by 6.7 million in 2012 to 1.354 billion people, excluding Hong Kong, Macau and Taiwan, the National Bureau of Statistics said.

Almost 118 boys were born for every 100 girls.

The working-age population -- defined as those from 15 to 59 -- fell by 3.45 million to 937 million, adding to concerns about how the country will provide for the elderly, with 194 million people now 60 or over.

It was the first absolute drop in the working-age population in "a considerable period of time", said National Bureau of Statistics director Ma Jiantang, adding that he expected it to "fall steadily at least through 2030".

China's wealth gap and population imbalances are major concerns for the ruling Communist Party, which places huge importance on preserving social stability to avoid any potential challenge to its grip on power.

Hundreds of protests break out across China every year, sparked by a wide range of social issues, including wage disputes and rural workers being denied residents' rights in cities.

China's urban population rose to 712 million, up 21 million on the previous year and adding to the strains on public services, while the rural population fell 14 million to 642 million.

Average per capita income was 26,959 yuan ($4,296) in the cities, compared to 7,917 yuan in the countryside, the statistics said.