BEIJING - China still faces major challenges in improving its air quality nationwide, said Li Ganjie, vice minister of environmental protection, at a press conference on Wednesday.

Only three cities, or 4.1 percent, of the 74 major Chinese cities subject to air quality monitoring met the national standard for good air in 2013, Li said.

The 10 most polluted cities in 2013 included seven in north China's Hebei Province, Jinan of east China's Shandong Province, Xi'an of northwest China's Shaanxi Province and Zhengzhou of central Henan Province. Most of these are located near Beijing.

Li urged addressing the key areas of industrial structure, energy efficiency, vehicle emissions and dust from construction sites in improving air quality.

Accumulation of air pollutants such as sulfur dioxide and nitric oxide also led to acid rain which mostly affected areas along the Yangtze River and southern side of its middle and lower reaches, accounting for 10.6 percent of the nation's land.

China has issued a five-year action plan to deal with air pollution.

The plan, unveiled by the central government in September 2013, stipulated cuts of coal use and the density of inhalable particulate matter, as well as the closure of polluting enterprises.

Li stressed the importance of timely disclosure of information and the public's participation in protecting the air.