People ride e-bikes in the thick fog in Handan, North China's Hebei province, on Nov 26, 2018. (Photo: IC)

BEIJING - China's national observatory Saturday renewed a yellow alert for thick fog that will shroud parts of the country.

Thick fog will envelop parts of Beijing, Tianjin and provinces of Hebei, Shandong and Henan on Saturday morning, according to the National Meteorological Center.

The visibility in parts of the areas will be reduced to less than 200 meters, the center said.

It suggests drivers in affected regions slow down, while airports, expressways and ports take appropriate safety measures.

China has a three-tier color-coded warning system for fog, with red being the most serious, followed by orange and yellow.