Chen Tian, chief of the Beijing Environmental Protection Bureau, said that about 28-36 percent of hazardous airborne particles known as PM2.5 came from surrounding provinces like Hebei, home to seven of China's 10 most polluted cities in 2013, according to official data.
The central government has identified the heavily industrialised Beijing-Hebei-Tianjin region as one of the main fronts in its war against pollution, and it is under pressure to cut coal consumption and industrial capacity.
Decades of unrestrained growth have hit China's environment hard and Beijing's often choking air has become a symbol of the pollution crisis.
Public anger over pollution in different places has sparked protests and while the government has announced plans to fight it, authorities often struggle to bring big polluting industries and growth-obsessed local authorities to heel.
Chen said that of the smog generated in Beijing, 31 per cent came from vehicles, 22.4 per cent from coal burning and 18.1 per cent from industry, according to China Environmental News, a publication of the Ministry of Environmental Protection.
Wang Junling, the vice head of the Beijing Environmental Protection Research Institute, said that while pollution from outside Beijing was a main component of its smog, the rapid growth of the city's population, energy use and economic output were also to blame for worsening air quality.
He told China Environmental News last month that from 1998 to 2012, Beijing's economic output rose 6.5 times and the number of vehicles rose 2.8 times. Over the same period, the city's population soared 66 per cent while energy consumption rose 90 per cent.
The city plans to cut coal consumption by 13 million tonnes by 2017, down from about 23 million tonnes in 2013. Hebei province used about 280 million tonnes of coal last year and aims to cut the total by 40 million tonnes over the same period.
Beijing also plans to limit the number of cars on its roads to 5.6 million this year, with the number allowed to rise to 6 million by 2017. It is also trying to enforce a ban on old vehicles with lower fuel standards.
The city government said in a report last week it failed to meet national standards in four of the six major controlled pollutants in 2013. It said its PM2.5 concentrations stood at a daily average of 89.5 micrograms per cubic metre, 156 per cent higher than national standards.
In 2013, PM2.5 concentrations in 74 cities monitored by authorities stood at an average of 72 micrograms per cubic metre (cu m), more than twice China's recommended national standard of 35 mg/cu m.