Forest fires that ravaged parts of Indonesia this year cost the country $US5.2 billion ($A7.6 billion), the World Bank says.
Total damage and economic losses as a result of the worst forest fires since 2015 are equal to about 0.5 per cent of Indonesia's gross domestic product and could cut growth in 2019 and 2020 by 0.09 and 0.05 percentage points, respectively, the World Bank says in a report released on Wednesday.
More than 620,000 hectares of forest, an area nine times the size of the capital Jakarta, burned between January and September in eight provinces, mainly on Sumatra and Borneo islands, the report says.
More than 900,000 people had reported respiratory health diseases, 12 national airports had halted operations and hundreds of schools in Indonesia, Malaysia, and Singapore had to temporarily close.
"Fires are considered the cheapest option among all methods to prepare lands for cultivation, or to claim lands in areas with disputes, where landownership is uncertain and where enforcement is weak," the World Bank says.
The bank said about 44 per cent of the areas burned this year were in peatlands, where fires are harder to suppress once started and release thick haze and carbon emissions into the atmosphere.
The carbon emissions from this year's blazes in Indonesia are estimated to be almost double the emissions from the fires in the Brazilian Amazon this year.
Forest fires are an annual hazard in Indonesia and the resulting haze often affects neighbouring Singapore, Malaysia and Thailand, driving air pollution to hazardous levels.
A study by researchers from Harvard and Columbia universities found that more than 100,000 people in Southeast Asia might have died prematurely in 2015 as a result of forest fires in Indonesia.
At least 25 people were killed in the 2015 fires, which caused economic losses estimated at $US16 billion.
Australian Associated Press