Heavy smog will persist in parts of Beijing, Tianjin, Hebei, Henan, Shandong, Shanxi, Shaanxi, Anhui, Jiangsu, Hubei, Jiangxi and Hunan from Wednesday morning to Thursday morning, according to the National Meteorological Center (NMC), which renewed an orange alert for those areas.

The NMC also renewed a red alert for fog in a number of northern, eastern and central regions.

From Wednesday morning to Thursday morning, thick fog in parts of Beijing, Tianjin, Hebei, Henan, Shandong, Anhui, Jiangsu and Shanxi will reduce visibility to less than 200 meters, it said.

In extreme cases, visibility may fall below 50 meters in those regions, it added.

China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.

Many Chinese cities have suffered from frequent winter smog in recent years, triggering widespread public concern. The central government has stepped up efforts to cut outdated production capacity and has dispatched inspection teams to provincial regions to supervise environmental measures at key industrial enterprises.