BEIJING - China will aim this year to reduce its emissions of sulphur dioxide by 6 percent from their 2005 levels as it steps up efforts to fight pollution, its top environmental official said in remarks published on Tuesday.

The official Xinhua news agency cited Zhou Shengxian, head of the State Environmental Protection Administration (SEPA), as saying that the government would close many small coal-fired power plants, as well as steel mills and cement plants, to cut emissions of the acid rain-causing pollutant.

Zhou also said the government aimed to reduce COD, or chemical oxygen demand, a measure of water pollution, by 5 percent from its 2005 level this year.

Many Chinese cities suffer from choking smog, including this year's Olympic host Beijing. The level of air pollution in the capital and its possible effects on athletes has been one of the biggest issues facing organisers of the Games.

Zhou said that Beijing would work with five other provinces and municipalities surrounding it to control air pollution during the Olympics, including by limiting traffic and shutting down polluting factories.

"We will make full use of the Olympic air quality coordinating teams this year to improve regional cooperation and implement relevant measures," Zhou said, according to Xinhua.

Authorities will step up the country's waste water treatment capacity by 12 million tonnes this year, with the aim of making sure all waste water in 36 major cities is treated by the end of next year, he said.

Sulphur dioxide and COD are primitive indicators of overall environmental health.

China has promised to cut the two pollution measures by 10 percent between 2006 and 2010.