International help to assist Indonesia in combatting forest and agricultural fires cloaking Southeast Asia in haze has begun to arrive on Sumatra island, an official said on Saturday.

Sutopo Purwo Nugroho, a spokesman for Indonesia's disaster mitigation agency, said a Bombardier amphibious aircraft and Malaysian crew arrived on Friday to begin water bombing South Sumatra.

"They are currently being briefed by the disaster mitigation chief and the water bombing will start immediately after that," Sutopo told AFP.

Fires in Sumatra and Kalimantan have been blanketing Southeast Asia for weeks, with pollution levels in both locations recorded far above hazardous levels. The haze has also forced Malaysia and Singapore to close schools and cancel outdoor events.

Singapore has also agreed to send a Chinook helicopter capable of pouring water from a huge hanging bucket, along with a Hercules C-130 carrying 42 firefighters from the city-state's Civil Defence Force.

The help from Singapore was scheduled to arrive in Sumatra on Friday but was postponed until Saturday due to poor visibility at the local airport.

Jakarta has deployed about 25,000 personnel and aircraft, but the firefighters have been overwhelmed by the extent of the blazes.

The Indonesian government insisted on not accepting international help for weeks before finally agreeing to accept the offers from several countries to combat the haze.

Australia has pledged to send a Lockheed L100 Hercules Air Tanker, with foreign minister Julie Bishop asserting Australia's experience in fighting the bushfires.