Kuala Lumpur - Air pollution in Malaysia's capital spiked to "very unhealthy" levels on Sunday as acrid smoke billowing from Indonesian agricultural fires intensified, in an environmental crisis that is fraying regional tempers.
Pollution readings soared past the 200-point level on Sunday morning in the Malaysian government's hourly air-quality index, a threshold that triggers automatic school closures during weekdays.
As the haze built up in Malaysia on Saturday, an airport just outside Kuala Lumpur closed temporarily in the afternoon as visibility dropped to less then 400m.
The closure forced at least 20 flights to be cancelled, according to Malaysian media reports, and followed Singapore's shuttering of schools on Friday as air there worsened to "hazardous" levels.
Parts of Indonesia, Malaysia and Singapore have been shrouded for weeks in a choking smoke haze from tinder-dry parts of Indonesia's Sumatra island.
The haze crisis - the worst since mid-2013 - grips the region nearly every year during the dry season, when agricultural land is illegally cleared by burning.
Indonesia has faced pressure from its neighbours to address the problem since it first emerged about 20 years ago.
But the issue has persisted, especially as plantations have expanded, driven in large part by rising global demand for palm oil, a key ingredient in a vast range of everyday consumer products.