BEIJING, Jan. 24-- Beijing will keep a tight rein on population growth this year as the city makes comprehensive efforts to solve serious urban problems like air pollution and traffic congestion, the mayor said in a governmental Work Report.

Population control is the thorniest problem, and it's directly tied to other issues, said Mayor Wang Anshun during a group discussion with deputies of the Beijing people's congress.

Beijing's population grew to 21.52 million by the end of 2014, making it one of the most populous cities in the world. Last year, 368,000 people were added, the smallest number since 2011 but still significant.

Around 8.19 million migrants lived and worked in the capital last year. The growth of migrants has slowed by about 1.7 percent, resulting in 129,000 fewer than the growth in 2013, the Work Report said.

To limit population, Beijing's local governments will implement a plan based on market strategies under the law, Wang said. It will mean moving some polluting industries out of the city, along with some labor-intensive ones. The labor force supporting those industries will move with them, he said.

On the other side of the coin, Wang said Beijing will look into adopting a system of credits for migrant workers, such as the system in place in Shanghai and other cities, based on various criteria including taxes paid and duration of residency. Achieving a certain credit score would allow a migrant to claim permanent residency.

Moreover, the municipal government will continue to work with Beijing's 16 districts and counties to implement population controls in 2015, Wang said.

This year, around 300 companies in polluting industries such as furniture manufacturing and other industries will be phased out, and another 36 large markets including those that sell clothing and household goods, such as the wholesale market near Beijing Zoo, will be moved.

A number of deputies voiced their concerns about the growing population and expressed support for the redistribution effort.

"We cannot flatly forbid migrant workers from coming. Relocating the industries and removing the markets is the way forward. This will be effective, but it will take time," said Zhang Cuixi, a deputy from west Beijing's Shijingshan district.

City data show that around 72 percent of employees are concentrated in downtown areas－a major source of traffic congestion and air pollution.

Zhang said the government should improve the basic facilities of each district, which would reduce traffic and environmental burdens. But she also acknowledged that it is likely to take a long time to solve all the problems.

Xu Nenxia, a deputy from Xicheng district, agreed, saying that population control comes with challenges－including at least one new trend: Some workers who have left the capital are returning.

"More of them found they can't get accustomed to the working and living conditions in their hometowns. The capital, with its good job opportunities, is still attractive to them," she said.