BAD AIR DAY: Smog shrouding the Olympic clock (right) outside the Great Hall of the People in Beijing last month as the city rushes to enforce more stringent pollution checks before the Games. -- PHOTO: AFP

The order, which has been talked about for years but formally announced only yesterday, will likely be followed up with a plan to keep half the city's cars off the roads during the Games, which run from Aug 8 to 24.

But officials declined to give details about the potential environmental impact of these measures, such as whether they would reduce current pollution levels significantly.

'We can only tell once we get more accurate calculations after the Olympics,' Mr Du Shaozhong, deputy director of the Beijing Environmental Protection Bureau, told reporters at a press conference.

Beijing has spent billions of dollars to improve its environment since winning the bid to host the Olympics seven years ago. But there are concerns that the efforts might have been negated by rapid urbanisation and a spike in car ownership in the city.

Athletes in endurance events are said to be considering wearing masks during their Olympic events, while the world-record holder in the marathon, Haile Gebrselassie of Ethiopia, has said he would skip the Games due to concerns over Beijing's air.

However, it is unclear if the sweeping order issued yesterday would come in time to reassure the athletes.

According to the document, all major construction work - identified as excavation and the pouring of concrete - would be suspended from July 20 to Sept 20.

During this period, work at all cement manufacturers, concrete mixing plants and limestone production facilities in south-eastern Beijing would also be halted 'in principle'.

At least 19 heavy-polluting factories and four coal- fired power plants must reduce their emissions by an additional 30 per cent. Even outdoor spray-painting would be banned during this period.

Mr Du side-stepped questions on the economic cost of the ban as well as queries over how - or if - affected industries and workers would be compensated.

A statement from the organisers of the Beijing Games acknowledged that these measures would raise production costs in the short term, but argued that they would make these 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.

And if the measures announced yesterday are insufficient, or if Beijing is hit with extremely bad weather conditions during the Olympics, officials said they would take 'more stringent measures'. But Mr Du did not give details of what these steps would be.

Meanwhile, Beijing will also be at the epicentre of a massive seven-month security operation beginning this month, the official Xinhua news agency reported yesterday, citing an announcement from the Ministry of Public Security.

No specific threat has been identified, though security issues have emerged as a bigger concern than previously assumed following recent revelations about alleged terrorist plots by separatist groups in Xinjiang, as well as the recent unrest in Tibet.

However, the ministry has identified eight general areas where security would be stepped up, including checks at hotels, entertainment outlets and key government offices. Officials have also been tasked with better securing the safety of major gas and oil pipelines.

Beijing, where most of the Olympic events will be held, has seen a stepped-up police presence since the beginning of the year.

chinhon@sph.com.sg