JAKARTA, Indonesia - Smoke from brush fires forced officials to cancel flights and drivers to use their headlights in the daytime Sunday in western Indonesia, while the air quality improved in neighboring Singapore and Malaysia.

The illegal brush fires were started by farmers or agricultural companies on Borneo and Sumatra islands as a cheap way of clearing the land.

The haze is a perennial problem for the region. The worst case occurred in 1997-98, when smoke from land-clearing in Sumatra blanketed much of the region and was blamed for losses of nearly $9 billion in tourism, health and business.

Visibility was down to 160 feet Sunday in Indonesia's part of Borneo island. Flights were canceled in the three provinces of South Sumatra, Riau and Jambi.

"We had to cancel all flights to avoid plane crashes and for passenger safety," Basuki Mardianto, the head of Sultan Taha Airport of Jambi province, told The Associated Press.

The pollution monitoring index, measured in downtown Palangka Raya, the capital of Central Kalimantan province, stood at "dangerous" as thick smoke penetrated windows and doors, forcing people to wear masks inside, the Antara state news agency reported. One official said highly flammable peat soil blazes in the region were out of control and had worsened the air quality.

In Singapore, the National Environment Agency reported an air pollution reading of 34 - which it rates as "good" - Sunday after it soared into the "unhealthy" range Saturday when the index was at a nine-year-high reading of 150.

In Malaysia, the air was also less polluted, the Department of Environment said, with six of the country's 51 monitoring stations recording unhealthy air quality, compared to 21 on Saturday.

Malaysia urged Indonesia to quickly ratify an agreement that would facilitate a regional response across Southeast Asia to the use of environment-damaging slash-and-burn methods by Indonesian farmers and plantation owners.

Indonesia is the only country among the 10-member Association of Southeast Asian Nations that has not ratified the ASEAN Agreement on Transboundary Haze Pollution, which was approved in 2002.

Malaysian Environment Minister Azmi Khalid called on Indonesia to prosecute any plantation company or farmers found responsible for lighting brush fires. "We implore Indonesia to impose the most severe penalties under their law to anyone found guilty," he said.