BEIJING, Dec. 18-- Chinese cities saw 63.6 percent of days with decent air quality in November, up 11.3 percentage points year-on-year, official figures show.

The 25 cities monitored in the Yangtze River Delta saw 68.8 percent of days with sound air quality, a 26.3 percentage point increase from the same period in 2013, according to a statement released Thursday by the Ministry of Environmental Protection.

Even the notoriously-polluted Beijing-Tianjin-Hebei region reported 42 percent of days with "good" or "fine" air quality, up 2.9 percentage points from the same period last year.

The region saw 22.4 percent of days with air quality in the range of "heavy" and "grave."

The top ten polluted cities included seven in north China's Hebei Province, along with Shenyang and Harbin, two northeastern cities and Zhengzhou, capital of central China's Henan Province.

In general, the major air pollutant in the country was PM2.5, followed by PM10, the statement said.