Aside from Kuala Lumpur, other areas where haze reached unhealthy levels were parts of the states of Selangor, Kedah, Negeri Sembilan, Perlis and Penang.
Health officials warned residents with asthma and pulmonary problems to stay indoors until the air quality in their areas improves.
Meteorological department satellite images showed there were 390 fires in Indonesia's Sumatra province, from where winds blow the smoke to neighbouring Malaysia and Singapore. Thirty-one fires were also recorded in Indonesia's Kalimantan province on the island of Borneo.
Open burning is common in Indonesia's Sumatra and Kalimantan provinces as it is the fastest way to clear plantation and forestlands.