Haze caused by forest fires in neighbouring Indonesia blanketed parts of Malaysia including the capital, causing air pollution to hit unhealthy levels.
Haze is an annual problem during the monsoon season from May to September as winds blow the fumes from Sumatra across the Malacca Strait to Malaysia.
Skies over Kuala Lumpur Saturday were gloomy and visibility was described as poor by the Meteorological Department. With dry weather forecast for the next week, air quality is expected to deteriorate further.
The Air Pollutant Index reached 127 in the capital Kuala Lumpur, 144 in Port Klang, the Southeast Asian country's top port and 129 in the township of Shah Alam. Readings of 101-200 are considered unhealthy.
The Star newspaper Saturday said that the haze situation was expected to worsen with the "hot and dry spell in the Riau district of Sumatra set to peak over the next two weeks.
"As in previous years, several hotspots in central Sumatra in Indonesia are causing the haze," it said.
Haze builds up during the dry season, affecting tourism and contributing to health problems across the region.
Indonesia's government has outlawed land-clearing by fire but weak law enforcement means the ban is largely ignored.