The Beijing-Tianjin-Hebei region saw more days of severe air pollution in March than the monthly national average and worsening conditions since February, a report from the national environment watchdog said on Wednesday.

Thirteen cities in the region reached national air quality standards just over a third of the time in March, according to the monthly report on air quality released by the Ministry of Environmental Protection. The report covers 74 major cities. Although the proportion of days with good air quality was 1.7 percent higher than that in March of last year, showing slight improvement, the region still had more serious pollution than in February, it said.

Sixteen cities, including Baoding and Xingtai of Hebei province, experienced high pollution days more than half the time in March, said Luo Yi, head of the Environmental Supervision Bureau of the ministry.