"Schools in the region have been ordered to remain closed. Local authorities have distributed face masks to residents.
Even in Kuala Lumpur, where smog levels have so far remained moderate, visibility is now strongly reduced and the smell of thick smoke hangs in the air, correspondents say.
Kuala Lumpur resident Raj Ahmed told the BBC: 'You wake up in the morning and you can smell burnt wood - you look out the window and there is constant smog clouding the major landmarks that you would ordinarily see.
'If you go outside, it's like constantly standing close to a small barbecue.'"