A sandstorm that swept across Beijing and China's northern provinces is forecast to partially affect South Korea on Thursday, sending fine dust levels to "very bad" in parts of the country, a research institute said.

The severe yellow dust that blanketed China over the past two days is expected to pass north of South Korea, but part of it is expected to move southeast into the country Thursday afternoon, the National Institute of Environmental Research said.

The country's western region is forecast to come under the influence of the sandstorm and experience high levels on the PM10 air quality index starting in the afternoon as the yellow dust, combined with existing fine dust, is likely to accumulate due to stagnant air currents.

The PM10 index measures the hourly concentration of pollution particles that are smaller than 10 micrometers and can enter the lungs.

The western port city of Incheon and northern parts of Gyeonggi Province that surround Seoul currently have "very bad" fine dust levels, while Seoul, southern parts of Gyeonggi and South Chungcheong Province may see their fine dust level worsen to very bad in the afternoon.

South Korea's weather agency categorizes concentrations of PM10 between 81 and 150 micrograms as "bad" and more than 151 as "very bad."

A yellow dust advisory has been in place across Gyeonggi and Incheon since Wednesday afternoon. (Yonhap)