BEIJING (REUTERS) - Eight northern Chinese cities failed to meet air quality targets in October and November, even as local authorities launched rigorous steps to cut emissions during the winter, the government said on Monday (Dec 11).

The failures highlight the challenge Beijing faces in cleaning the nation's notoriously toxic air during the winter when smog blankets colder regions as people crank up their heating.

The concentration of hazardous breathable particles, known as PM2.5, in Handan in Hebei province rose by an average of 8.8 per cent in October and November, the Ministry of Environmental Protection (MEP) said in a statement on Monday.

The city ranked at the bottom of 28 included in the government's six-month winter campaign to curb air pollution, which includes targets to cut PM2.5 by 10-25 per cent each month compared with last year's levels.

The MEP said the other cities failing to hit targets were: Jincheng and Changzhi in Shanxi province; Jining and Heze in Shandong; and Kaifeng, Puyang and Zhengzhou in Henan.

However, the data also showed that in November average PM2.5 levels across the 28 urban areas dropped by 22.6 per cent to 65 micrograms per cubic metre.

This year, Beijing has ordered millions of households to convert to gas or electric heating from coal and eliminated 44,000 coal-fired industrial boilers across the 28 cities included in the winter campaign.

But recent gas shortages have forced the MEP to scale back its ban on burning coal in some households, fuelling concerns over a possible rebound in air pollution.

"Local governments should reinforce inspections and take more targeted measures to ensure meeting the air pollution improvement targets," the MEP said in its statement on Monday.

It also warned that the coming three months will be crucial for its anti-pollution campaign, with weather conditions such as a lack of wind potentially making it more difficult to clear dirty air.