China's service sector activity expanded strongly in December, a monthly survey showed Friday.

The purchasing managers' index (PMI) for the non-manufacturing sector came in at 54.4 in December, up from 53.6 in November and also the highest in 2015, according to a report released jointly by the National Bureau of Statistics and the China Federation of Logistics and Purchasing.

A reading above 50 indicates expansion, while a reading below 50 represents contraction.