Stricter measures will be taken to monitor emissions and punish violators as the government tries to reduce pollutants from small factories in northern parts of the country, Chen Jining, minister of environmental protection, said on Friday.

Large enterprises in the Beijing-Tianjin-Hebei region have been put under environmental supervision, which, as a result, has seen their emissions decline sharply.

However, many small factories are continuing to discharge pollutants, which are partly to blame for the severe smog that has covered most parts of North China in recent days.