JAKARTA: Indonesia warned on Friday that haze from forest fires was floating across the Malacca Strait toward its neighbours, and that the number of blazes was rising.
The fires and resulting smog are an annual dry season problem, when blazes are started illegally to quickly and cheaply clear land, typically to make way for palm oil and pulpwood plantations.
But last year's haze outbreak was among the worst in memory, shrouding Malaysia, Singapore and parts of Thailand in acrid smoke. The crisis forced school closures and caused thousands to fall sick across the region.
The annual ritual is about to begin again, with Indonesia's neighbours complaining bitterly, officials from the affected countries meeting, and Jakarta vowing to seriously enforce the laws against illegal burning.
While this year's fires have yet to reach the levels of 2015, the number has been rising in recent weeks as Indonesia heads toward its peak dry season in September.
Disaster agency spokesman Sutopo Purwo Nugroho warned that smoke on Thursday had started floating across the Malacca Strait, which runs between Indonesia, Malaysia and Singapore.
"Smoke from forest and land fires in Riau (province) has started to enter the Malacca Strait," he said in a Twitter message. "Let's prevent and put out the fires."
Riau, on western Sumatra, is a major centre of the palm oil and pulpwood industry, and many fires occur there every year.
He also said the number of "hotspots" detected by satellites -- areas of intense heat that are either already on fire or vulnerable to going up in flames -- had increased in West Kalimantan province, on Indonesia's part of Borneo island.
A total of 158 hotspots were detected in the province on Friday, up from 106 a day earlier.
The governor of the province, a centre of the palm oil industry, had asked the disaster agency to provide helicopters for water-bombing and "cloud-seeding", or chemically inducing rain, said Nugroho.
Jakarta has announced a plan to stop granting new land for palm oil plantations, and established an agency to restore millions of hectares of carbon-rich peatlands susceptible to fires.