BEIJING -- Chinese mainland's population has increased to 1.373 billion by Nov 1, 2015, 33.77 million more than in 2010, when the sixth national census was conducted, the National Bureau of Statistics (NBS) said Wednesday.

According to the report of a sample survey conducted by the NBS, the annual average growth rate was to 0.5 percent over the past five years (2010-2015), lower than the 0.57-percent growth rate during the 2000-2010 period.

Males accounted for 51.22 percent of the total population, while females made up 48.78 percent, the report said. The male-to-female ratio was 105.02, lower than the 2010 ratio of 105.2.

The population living in urban areas totaled 767.5 million, or 55.88 percent of the total, up by 6.2 percentage points from the 2010 figure, while the population categorized as rural fell to 605.99 million.

The sample survey covers 21.31 million people, accounting for 1.55 percent of the total population, the NBS said.

In a separate development, authorities on Wednesday warned that China's gender ratio at birth remained high, and vowed to tighten controls on medical equipment and medicine that could be used in pre-birth gender tests and sex-selective abortions.

China has the worst gender imbalance in the world. The National Health and Family Planning Commission said last year this was a direct result of illegal pre-birth gender tests and sex-selective abortions.

Gender tests on fetuses and sex-selective abortions are a crime in China. Nonetheless, the preference for sons, and previous family planning regulations have driven both practices.

Latest figures suggested that the country's birth sex ratio stood at 113.51 in 2015, down from 121.18 more than a decade ago in 2004.