In Beijing's blueprint, high ranking officials said its population should not exceed 23 million by 2020.

According to the 13th Five-Year Plan (2016-2020), permanent residents should not exceed the number of 23 million. The capital's population reached 21.7 million by the end of last year.

Lu Yan, director of Beijing Municipal Commission of Development and Reform, said at a press conference Saturday, "Considering the crowded downtown area, the population must be controlled; some will be relocated out of town."

The city's mayor Wang Anshun said Friday that the population of six downtown districts will drop 15 percent in five years.

From 2010 to 2014, the capital's population increased by 1.52 million, 53 percent of which were located in the six downtown districts – Dongcheng, Xicheng, Chaoyang, Haidian, Shijingshan and Fengtai - said Lian Mingyu, president of International Institute of Urban Development.