Beijing: Growth in China's manufacturing sector slowed slightly in December as a punishing crackdown on air pollution and a cooling property market start to weigh on the world's second-largest economy.

The data support the view that the economy is beginning to gradually lose steam after growing by a forecast-beating 6.9 per cent in the first nine months of the year, but the findings did not appear to suggest a risk of sharper slowdown at this point.

The official Purchasing Managers' Index (PMI) released on Sunday dipped to 51.6 in December, down from 51.8 in November and in line with forecasts from economists in a Reuters poll. But the overall reading still appeared relatively solid, and marked the 18th straight month that the sector has expanded. The 50-point level divides growth from contraction on a monthly basis.

The figures showed that China's full-year 2017 economic growth would be about 6.9 per cent and around 6.5 per cent for 2018, according to the China Federation of Logistics and Purchasing, which compiles the data. Both predictions would be slightly stronger than those in a Reuters poll.

Boosted by hefty government infrastructure spending, a resilient property market and unexpected strength in exports, China's manufacturing and industrial firms have been a major driver behind solid economic growth this year.

However, a slowdown has started to take hold in the last few months because of a wide-ranging combination of government measures, from a crackdown on smog in heavily industrialised northern provinces to continued curbs on the housing market.

Chinese steelmakers in 28 cities have been ordered to curb output between mid-November and mid-March, while a campaign to promote cleaner energy by converting coal to natural gas has also hampered manufacturing activity in some cities.