The yellow storm had spread to almost all of the country as of 7 a.m. and will affect the entire nation until Thursday, according to the Korea Meteorological Administration (KMA).
A fine dust advisory was issued for all parts of South Korea, Yonhap News Agency reported citing authorities as saying.
The average hourly concentration of fine dust particles smaller than 10 micrometers in diameter, known as PM 10, had risen to 192 micrograms per cubic meter in Seoul as of 7 a.m. and 494 micrograms in the city of Ulsan, 307 km southeast of Seoul, the KMA said.
[bsa_pro_ad_space id=1]A fine dust advisory is issued when the PM 10 figure stays above 150 micrograms for longer than two hours.
In a related move, the Ministry of Environment said the second-lowest level of "caution" in the government's four-stage crisis alert against yellow dust was enforced for almost all parts of the country as of 7 a.m.
The PM 10 density will remain at the "very bad" level in the rest of the country until Thursday, the KMA said.
The authorities advised people with respiratory illnesses, the elderly and children to stay indoors, and use masks when going outside.
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