BEIJING, Sept. 27 -- By 2020, the size of resident population in Beijing should be controlled to within 23 million and kept at this level thereafter, according to a city planning document for Beijing issued by China's central authorities.

Moreover, construction land in the city should be reduced to about 2,860 square km by 2020 and to 2,760 square km by 2035, the document said.

The Communist Party of China (CPC) Central Committee and the State Council has approved the general city plan for Beijing during the period between 2016 and 2035, submitted by the CPC Beijing Municipal Committee and Beijing municipal government.

The approval was made public on Wednesday.

Wednesday's document said the environmental and resource capacity is the rigid limit for the city's size and measures should be taken to reduce the stress of the city.

The document said control of population and construction will force the city to transform its development mode, upgrade and transform industries, and optimize and adjust its city functions.

The document pledged a "strictest" management of water resources.

Also, the height of the buildings in the city center should be strictly controlled, the document said.

Noting that Beijing is the capital of China and a center of politics, culture, international exchanges and scientific and technological innovation, the document stressed security of the city to ensure a good environment for the work of central authorities.