Beijing's concentration of fine air pollution particles — PM2.5 — averaged 38 micrograms per cubic meter for 2020, the best air quality for the city since 2013, authorities announced on Monday.

Beijing saw 276 days with good air quality last year, 36 days more than in 2019, the Beijing Ecology and Environment Bureau said at a news conference on Monday.

According to the bureau, it is the first recorded time that Beijing's annual average PM2.5 density dropped below 40 micrograms per cubic meter.

Compared with the 2013 level, Beijing's annual average PM2.5 density dropped by 57.5 percent in 2020.

Beijing government said it will continue to focus on key sources of pollution, including heavy diesel vehicles, volatile organic compounds and dust.

Meanwhile, it will strengthen cooperation with regional areas, including North China's Hebei province and Tianjin city, to improve air quality.