BEIJING -- Nearly one in every five Chinese people were rural migrant workers -- those from rural areas working in cities -- by the end of last year, official statistics showed on Friday.

The number of rural migrant workers increased 3.9 percent to 262.61 million by the end of 2012, accounting for 19.39 percent of the country's total population, the National Bureau of Statistics said in a report on China's development.

In breakdown, rural workers employed outside their hometowns rose 3 percent from a year ago to 163.36 million in 2012, while those employed in their hometowns rose 5.4 percent to 99.25 million, the report said.

Migrant workers have emerged along with China's fast economic expansion since the implementation of the reform and opening-up policy more than three decades ago. As China becomes urbanized and industrialized, huge labor demand and opportunities in cities have drawn millions of people to leave their homes.

Helping rural workers become urban residents is considered by the government as an important task for the country's urbanization, according to this year's first policy document released last month by the State Council, or the cabinet.

China will push forward reform of its household registration system, loosening requirements for obtaining residency permits in small and medium-sized cities and small townships, the document said.

The country will also intensify efforts to provide professional training for migrant workers, ensure their social security and protect their rights and interests, according to the document.