China on smog alert

China's weather observatory on Tuesday issued a yellow alert for smog that is expected to shroud a big part of north China.

The National Meteorological Center (NMC) forecast that smog will blanket part of Beijing, Tianjin, Hebei, Shandong, Henan and Shaanxi from Tuesday night to Wednesday.

Burning straw in farmlands in Hebei and Henan partly contributed to the smoggy weather, according to the NMC.

A cold front will sweep these areas from north to south starting Saturday night and it is expected to disperse the smog.

The weather observatory warned drivers of low visibility and advised people to stay indoors.

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