China's national observatory on Sunday renewed a yellow alert for thick fog in some northern and eastern regions.

On Sunday morning, thick fog will affect Beijing, as well as provinces of Hebei, Shandong, Henan, Anhui, Jiangsu and Zhejiang, reducing visibility in some areas to less than 200 meters, the National Meteorological Center said.

The center said drivers in affected regions should slow down, while airports, freeways and ports should take appropriate safety measures.

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