BEIJING - Air pollution in the Chinese capital Beijing and its neighbors Tianjin and Hebei was heavier than other parts of the country in August, the environmental watchdog announced on Tuesday.

The 13 monitored cities in the region had on average 65.4 percent, or about 20, of the 31 days in August failing to meet the required standards set by the Ministry of Environmental Protection, while the national average stood at around 10 days.

The ministry quoted O3 and PM2.5 - airborne particles measuring less than 2.5 microns in diameter that can pose health risks - as the major pollutants in the region.

Air quality in 74 monitored cities met the standard in 66.7 percent, or 20.68, of the 31 days in August. This is down four percentage points from the previous month, the ministry said in a report.

These cities had on average 0.56 heavily polluted days, or 1.8 percent of the days last month, up 0.2 percentage point from July.

East China's Yangtze River Delta and South China's Pearl River Delta had more clear days than other parts of the country with 67.2 percent and 76 percent meeting the standard respectively in August, according to the report.

The country has been under growing pressure to address the causes of air pollution after heavy smog smothered large swathes of the country early this year.

In a government action plan unveiled last week, China vowed to take a multi-pronged approach to tackling air pollution by cutting coal use, shutting down polluters and promoting cleaner production.

PM2.5 should fall by about 25 percent from 2012 levels in Beijing and surrounding provincial areas by 2017, according to the plan.

China has about 496 air quality observation points in 74 cities in 2012.