Indonesia launched Friday its biggest operation ever to combat fires blanketing Southeast Asia in haze, an official said, with dozens of planes and thousands of troops battling the widespread blazes.

Thirty-two planes and helicopters -- including six aircraft from Singapore, Malaysia and Australia -- were dispatched to back up the more than 22,000 personnel on the ground who have been fighting the fires for weeks.

Indonesian National Disaster Management Agency spokesman Sutopo Purwo Nugroho said the air teams would conduct water bombing and weather modification efforts across six of the worst-hit provinces in Sumatra and the Indonesian portion of Borneo island.

"This is the biggest haze emergency operation ever carried out by the Indonesian government," the spokesman said.

For weeks, fires illegally started to clear land for plantations have shrouded Indonesia, Singapore and Malaysia in acrid smog, worsening air quality, closing schools and forcing the cancellation of outdoor events.

The blazes are an annual occurrence during the dry season, but scientists have warned this year's are on track to be the worst ever as an El Nino weather system has created tinder-dry conditions in Indonesia.

Jakarta earlier this month agreed to accept international help after weeks of failed attempts to douse the blazes infuriated its neighbours.

Japan on Friday joined several other countries contributing to the emergency effort, donating two tonnes of flame retardant to Indonesia.

Nugroho said dry conditions were continuing to hamper efforts, with new fires still popping up. Indonesian satellites as of Friday had detected more than 750 hotspots on Sumatra, mostly in the south of the island.