The country's environmental watchdog has vowed to tighten its supervision of polluting enterprises nationwide to further improve air quality.

The Ministry of Environmental Protection fined more than 1,800 industrial enterprises for unlawful conduct during an inspection campaign from November to February.

Warnings and fines were issued to 2,185 construction sites with excess dust pollution, 1,848 underground oil refining workshops and coking plants, and 14,122 restaurants without oil fume purification facilities during the investigation.