The illegal burning of forests and other land on Indonesia's Sumatra island to clear space for palm oil plantations is a chronic problem during the June-September dry season, the ABC reports.
The haze caused by fires on Sumatra has also shrouded neighbouring Singapore, though air quality in the city state has improved over the weekend after reaching hazardous levels.
Malaysia's minister for natural resources and environment, G. Palanivel, said in a Facebook the air pollution index had exceeded 750.
Any reading above 300 indicates hazardous air pollution.
The Johor state operations centre said residents in the affected areas of Johor state, Muar and Ledang, have been advised to stay indoors
