"In case of extremely negative meteorological conditions or severe air quality, we will take even more stringent measures," he said.


Du said further measures would be taken in neighbouring Tianjin, Hebei, Inner Mongolia, Shanxi and Shandong.


Details of traffic restrictions aimed at taking half the city's cars off the roads during the Games from Aug 8 to 24, would be released later.


China also announced on Monday a seven-month security operation starting this month, largely focusing on Beijing.


The public security ministry have identified several areas where security would be stepped up, including hotels, entertainment outlets, key government offices and major gas and oil pipelines.


Construction work involving excavation and the pouring of concrete will be suspended for the two months.


Heavy polluters targeted


Cement manufacturers, concrete mixing plants and limestone production facilities in southeastern Beijing are all supposed to stop work.


And 19 heavy polluters, including steel factories and coal-burning power plants must reduce their emissions by 30 per cent.


Construction work involving excavation and
pouring of concrete will be halted [AFP]
But Du declined to give details about how much the measures were expected to reduce current pollution levels, saying accurate calculations would only be available after the Olympics.


The head of the International Olympic Committee, Jacques Rogge, has said that pollution in Beijing will not endanger the health of athletes, although their performance might suffer.


"It might be that some will have to have a slightly reduced performance, but nothing will harm the health of the athletes. The IOC will take care of that," Rogge said this month.


But assurances by him and officials in Beijing have not stopped Haile Gebrselassie, the marathon world-record holder, from announcing he would skip the Games because of concerns over Beijing's air quality.


Other athletes in endurance events are said to be considering wearing masks during their races.


Economic cost


Du was vague about the economic cost of the anti-pollution measures and whether affected industries and workers would be compensated.


A statement from the Games organisers acknowledged that the measures would raise production costs in the short term, but argued that they would make the affected companies more competitive in the long run.


"For this reason, the Beijing municipal government is focused on the 'big picture', and all governmental bodies are working hard to shoulder the responsibilities of economic and social development as well as environmental protection," the statement said.


Du said the long-term work for reducing emissions was to the benefit of the companies and any compensation would be decided when they discuss their annual plans with local government.


"In the short-term it will cost them, in the longer term it will accelerate the upgrade of their technology," he said.


Companies that shut down or restrict production for the two months would be exempt from pollution emission charges, Du added.


Beijing has denied charges that the city's pollution monitoring formula has been changed to allow the Olympic host to meet environmental standards.