The density of fine dust particles smaller than 10 micrometers in diameter, known as PM 10, will rise to "very bad" levels in Seoul and many other parts of South Korea, beginning Friday evening, due to the influx of yellow dust originating from deserts in northern China and Mongolia, a state forecasting agency said.

The PM 10 reading is to soar above the government-designated "very bad" level in the greater Seoul area and central and southern provinces, including Gangwon and Chungcheong, late Friday, according to the state-run National Institute of Environmental Research's Air Quality Forecasting Center.

On Saturday, all of South Korea will be blanketed by very bad levels of PM 10 particles, the center said. The weather authorities here categorize concentrations of PM 10 between zero and 30 micrograms as "good," between 31 and 80 as "normal," between 81 and 150 as "bad" and more than 151 as "very bad."

As of 1 p.m., the daily average concentration of PM 10 reached 44 micrograms per cubic meter in the southeastern city of Daegu, 40 micrograms in Gyeonggi Province that surrounds Seoul, 39 micrograms in Sejong and 31 micrograms in Seoul, the center said.

The center said the PM 10 figure will remain at bad levels in almost all parts of the country under the influence of a massive dust storm that originated in the Inner Mongolian region in northern China and in Mongolia on Wednesday and moved south by riding northwesterly winds.

Only about two weeks ago, South Korea was hit by an extraordinarily strong yellow dust storm originating from the same deserts in northern China and Mongolia. (Yonhap)