Shanghai lifted its air pollution alert on Sunday as heavy smog that had lasted for days began to disperse away.

The eastern metropolis remained hazy on Sunday morning but the city's weather center said the low visibility was more a result of moist fog rather than the fine particles in smog.

The smog has considerably lessened, the center said. The city's air quality stood at "medium pollution" on Sunday, but environmental officials said a cold front will bring strong winds on Monday to clean up the air.

The foreseeable end of smog brought relief to the city, which has spent a week cloaked in choking smog, with Air Quality Index (AQI) topping 500 in certain areas. AQI of over 300 is defined as "serious pollution".

The smog has interrupted traffic, delayed flights, prompted a ban on outdoor school activities and citizens have snapped up facial masks.

Large parts of China have seen smoggy weather since the start of December. China Meteorological Center on Sunday upgraded its smog alert to orange, the second highest in its four-tier warning system, as it warns of heavy smog in provinces of Jiangsu, Zhejiang, Anhui, Hebei and Shandong.