A thick haze caused by fires in Indonesia has disrupted internal air services and forced flight cancellations in Malaysia's Sarawak state on Borneo island, an airport official said.

National carrier Malaysia Airlines has been forced to cancel several flights by small aircraft since Thursday as air quality had deteriorated, said a spokesman for Sarawak's Miri Airport on Saturday.

He said that a number of flights servicing the state's rural areas had to be delayed or cancelled as smaller aircrafts which fly at lower altitudes could not land or take off in the hazy conditions. "The air quality has gotten very bad and the low visibility makes flying the small planes very dangerous," the spokesman told AFP.

He said air routes connecting the Malaysian peninsula to Sarawak were unaffected as they were serviced by bigger aircrafts that were not hindered by the haze.

Local newspapers have reported an increase in fires in the Indonesian regions of Kalimantan on Borneo and Sumatra, which are attributed to both deliberate land clearance and accidental outbreaks.

There were 203 hotspots – areas showing high levels of heat caused by burning – detected in Sumatra Friday, up from just 60 the day before, the New Straits Times daily reported.

A spokesman from the Meteorological Department here told AFP that visibility levels in Sarawak and its neighbouring Sabah state on Friday were "one of the worst in years".

"The visibility in those states is alarmingly low, and it could cause serious problems, aside from disrupting flight services," the spokesman said.

"Everything has to be put on hold when the haze gets this bad, from agriculture to schooling, for health and security reasons." The spokesman said it was too soon to tell if the haze would improve, but added that little rain was expected in Sabah and Sarawak in the coming week.

"This is the dry season and every year it's the same thing. The burning in Sumatra and other parts of Indonesia causes us to be hit by the haze," he said.

In 1997 and 1998, choking haze caused by forest fires in Indonesia enveloped parts of Southeast Asia for months, causing serious health problems and traffic hazards and disrupting airline schedules. The haze then cause an estimated 9.3 billion dollars in economic losses.