Yellow sand blanketing the Chinese capital Beijing is preventing many residents from going out, as air pollution remains at its worst levels in the city.

Chinese weather officials say they observed the yellow sand in wide regions of northern China on Thursday. The sand particles are blown from deserts in inland regions and neighboring Mongolia.

The airborne sand is a spring weather phenomenon in East Asia. Beijing residents began to see yellow dust in the air from around Monday.

The air quality in the Chinese capital again hit the worst level on the country's six-tier scale on Thursday.

Visibility continues to be poor. Buildings in the distance are blurred in a yellowish haze.

Home-delivery service workers say they are busy as they have more food orders than usual. But they also say they must be careful riding their bikes. One worker says he cannot keep his eyes fully open because of the dust, and has to slow down due to poor visibility.

Weather officials in Beijing say the yellow sand will continue to affect the city until Friday night.

They are calling on residents to keep windows shut, and to use masks, scarves and other items when going out to protect their eyes and mouths.