Beijing witnessed an increasing number of days with blue skies in 2014, a clear improvement in air pollution control, while the reduction in the average concentration of PM2.5, a major air pollutant, failed to reach the annual goal by a hair, the municipal environmental watchdog said on Sunday.

This year, Beijing will continue to keep a tight rein on air pollutants. It aims to reduce the concentration of PM2.5 - airborne particles smaller than 2.5 microns in diameter that can penetrate the lungs and harm health - by 5 percent, a goal that the capital is confident of reaching.

Last year, Beijing had 204 days with air quality exceeding the national standards - 20 days more than in 2013. In addition, there were 45 days with heavy pollution - the average concentration higher than 150 micrograms per cubic meter - down from 58 days in 2013, according to the report of the Beijing Environmental Monitoring Center.