Kuala Lumpur marathon cancelled as city turns grey with smog from Indonesian forest fires

One of Malaysia's biggest marathons was cancelled on Saturday over fears the health of more than 30,000 runners was at risk from thick smoke caused by Indonesian forest fires that have sparked a regional environmental crisis.

Organisers of the Standard Chartered Kuala Lumpur Marathon set for Sunday said it would not be held due to worsening air quality in Kuala Lumpur, which was shrouded in an acrid grey haze from the slash-and-burn fires.

The haze has afflicted large swathes of Southeast Asia for weeks, sparking health alerts,school shutdowns and affecting flights.

Robert Field, a Columbia University scientist based at NASA's Goddard Institute for Space Studies, has been quoted by the space agency as saying that a possible longer dry season might make the 2015 haze crisis "the most severe on record¨.

Scientists predict the current crisis could surpass 1997 levels, when out-of-control fires sent pollution soaring to record highs in an environmental disaster that cost an estimated US$9.0 billion.