BEIJING, Jan. 7 -- China's 31 provinces, municipalities and autonomous regions have been set targets to reduce main air pollutants by 5 to 25 percent, in the country's latest effort to combat pollution.

Among the provincial-level regions, eleven were given PM2.5-reducing tasks, including an annual 25 percent decrease, the highest, for Beijing and neighboring Tianjin municipality and Hebei Province, according to a liability paper signed Tuesday by the regions and the Ministry of Environmental Protection.

Shanghai, Jiangsu, Zhejiang, Shandong and Shanxi will have to cut the indices by 20 percent, followed by 15 percent for Guangdong and Chongqing and 10 percent for Inner Mongolia Autonomous Region.

The other regions were ordered to cut their PM10 readings by 5 to 15 percent, with only Hainan and Yunnan provinces and Tibet Autonomous Region, where air pollution is relatively slight, given no specific goals but "continuous improvements" must be made.

PM2.5 refers to airborne particles measuring less than 2.5 microns while PM10 gauges particulate matter under 10 micrometers. Both are main air pollution indicators.

The paper also urged regions to take various measures such as reducing the use of coal, eliminating outdated industrial capacity as well as better management and control of heating boilers, vehicles and dust.

Local governments have been ordered to map out detailed plans to ensure the implementation of various anti-pollution methods and lay down specific goals for each year.

Meanwhile, the State Council, or China's Cabinet, is mulling a system to evaluate each provincial-level government's progress, and those failing to reach their goals will be named and shamed. They will have to provide explanations and make corrections.

Despite a wide spectrum of measures including severer punishment for industrial polluters and the auction and lottery of car license plates, a government report revealed last month that progress was lagging in four environmental targets, including carbon dioxide emissions and energy consumption.

In the relatively more polluted northern area, Beijing reported 58 days of heavy air pollution last year, or roughly one heavy pollution day in every six.