JAKARTA (DPA) - The Indonesian military deployed an aircraft to create artificial rain on Monday (Feb 25) as thick smog caused by forest fires forced schools to close on Sumatra island, officials said.

"The plane can carry tonnes of salt to be used in cloud-seeding," said Edwar Sanger, the head of the civil protection agency in Riau province on Sumatra.

Haze has blanketed parts of Riau, forcing schools to send students home as pollution reached hazardous levels on Monday, Antara news agency reported.

Visibility in Rupat sub-district was as low as 100m, local official Hanafi was quoted as saying by Antara.

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 South-east Asia might have died prematurely in 2015 as a result of forest fires in Indonesia.

The research attributed premature deaths in adults to breathing high levels of carbon-based particulates.

The Indonesian government put the death toll from the 2015 forest fires at 24.

The World Bank estimated economic losses as a result of the fires at US$16 billion.