China will ratchet up planned steel production cuts and target illegal factories in an effort to reduce pollution during the winter, an official said on Wednesday.

Smog billows from chimneys and cooling towers of a steel plant during hazy weather in Taiyuan, Shanxi province, China, December 28, 2016.

Beijing launched a campaign to cut steel overcapacity early last year in an attempt to stem a supply glut and crack down on pollutants from non-compliant producers.

The government committed to cutting 100-150 million tonnes of annual crude steel capacity over five years, though critics say the curbs are yet to have a material effect.

State media agency Xinhua reported that 26 cities in northeast China will be required to meet annual goals to cut steel overcapacity by October, targeting illegal factories, citing Zhao Yingmin, vice minister of environmental protection.

Steel producing cities in China's Hebei province must also cut production in half during the winter season and seasonal production halts on cement and casting industries in the same region will remain in effect, Zhao was quoted as saying.

Earlier this month environment group Greenpeace released research in which it said the world's biggest steel producer actually increased production in 2016.

China's State Council warned in December of crackdowns on officials who fail to meet inspection standards.

Source: Reuters