Indonesia's disaster chief Tuesday rejected criticism his country was not doing enough to combat the haze crisis, saying every possible resource was being deployed to fight the forest fires blanketing Southeast Asia in smog.

Indonesia has come under growing pressure from its neighbours in recent weeks as thick smoke from fires on Sumatra and Kalimantan has sent pollution levels soaring in Malaysia and Singapore, where schools have been closed and major outdoor events cancelled.

The blazes flare annually during the dry season as fires are illegally set to clear land for cultivation. But an El Nino weather system has made conditions on track to become the most severe on record.

Malaysian Prime Minister Najib Razak has urged Indonesia to take action, saying only Jakarta has the authority to investigate the cause of the fires and convict those responsible.

But Indonesia has rejected suggestions it is not doing enough, with the country's disaster chief saying everything possible was being utilised.

"We have done the best we can," Willem Rampangilei told reporters.

"It is understandable if other countries are upset, but we Indonesians are more upset."

Pollution in Singapore and Malaysia has tipped beyond hazardous levels since the haze outbreak began last month, while concentrations more than five times that limit have been recorded on Kalimantan, Indonesia's half of Borneo island.

Singapore has offered to help combat the fires, volunteering a Hercules plane and IT expertise, but Indonesia has insisted it has the equipment necessary to do the job.

Rampangilei said Indonesia had four planes on standby to conduct cloud seeding, but conditions in the past week had stymied attempts to produce artificial rain.

Efforts by more than a dozen helicopters to waterbomb hot spots have several times been thwarted by thick smoke, he added.

Rampangilei said more troops and police would be deployed to fight the fires, while authorities were considering dumping 40 tonnes of fire retardant on smouldering peatlands.

More than 1,200 hotspots were still active in Sumatra and Kalimantan as of Tuesday, the disaster agency said, while around 140,000 people have reported respiratory infections due to the thick smog.