BEIJING (Bloomberg) - Air pollution reached "hazardous" levels in Beijing on Sunday (Nov 29), prompting the city to upgrade to the second- highest alert for the first time in 13 months on the same day that the Chinese government said it has met pollution-reduction targets for the year.

Beijing municipal government lifted the air-pollution alert to orange at 10am on Sunday, according to the Beijing Municipal Environmental Monitoring Centre.

The concentration of PM2.5, the particulates that pose the greatest risk to human health, as of 9.34pm Saturday was 300 mg per cubic metre - which is about 12 times higher than World Health Organisation-recommended levels.

The air quality worsened on Sunday and the centre upgraded the alert without providing an updated pollution reading.

The Chinese government on Sunday said it had achieved its targets for reducing major pollutants outlined in its five-year plan ending 2015 ahead of schedule, according to Xinhua news agency.

Still, some major pollutants need to be cut by 30 per cent to 50 per cent to substantially improve environment quality, Xinhua cited Mr Chen Jining, the environment minister, as saying.

The current "severe pollution" in Beijing won't clear up for another two days, according to the environment bureau.

The city will ask some factories to suspend or limit production while the orange alert is active, it said.